Zoology 111.pdf

ZOOLOGY  CELL METABOLISM - One of the properties of a living organism is metabolism. This is the sum total of a'll the reactions in a body and for a living cell there are thousands of those reactions that would occur in it and those reactions are actually able to produce...

ZOOLOGY  CELL METABOLISM - One of the properties of a living organism is metabolism. This is the sum total of a'll the reactions in a body and for a living cell there are thousands of those reactions that would occur in it and those reactions are actually able to produce energy in which the cell will later on apply this every to perform work - an example of the conversion of energy is observed among these aquatic animals that would exhibit bioluminescence. When we say bioluminescence, they wil exhibit 11ght when it is dark. This organism is able to convert energy in the form of light and this through bioluminescence (squid) - the living cell is a miniature chemical factory where thousands of reactions occur - The cell extracts energy and applies energy to perform work - some organisms even convert energy to light, as in bioluminescence - Metabolism is theG totality of an organism's- chemical reactions ② - - metabolism is an emergent property of life that arises from interactions between molecules - within a cell -a metabolic pathway begins with a specific molecule and ends with a product -Each step is catalyzed by a specific enzyme. Specific enzyme specific to a specific reaction that could ease down metabolic rate how a product is produced out of a diff reaction that woul accur from a starting molecule - two types of metabolism: catabolic - Catabolic pathway release energy by breaking down complex molecules into simpler compounds --cellular respiration (catabolic pathway), the breakdown of glucose in the presence of oxygen is an example of a pathway of catabolism. Glucose will breakdown to produce ATP Ibiologicales - Anabolic pathwaysE - consume energy to0build complex = molecules from simple ones (opposite of catabolism). synthesis of smaller molecules - - in the presence of ATP, it will be able to produce a larger molecule. Consumption of energy to produce larger molecule -- - the synthesis of proteins from amino acids is an example of anabolism - bioenergetics is the study of how organisms manage their energy resources - we are made of organic molecules but we still need inorganic molecules I protein , carbs , fats , nucleiid (DNA and RNA) Since were talking about the different reactions that would occur in a living cell as well as its equivalent products that are actually produced by a certain reaction, this is what we call as redox reaction or oxidation and reduction Redox reduction: oxidation and reduction - The transfer of electrons during chemical reactions releases energy stored in - organic molecules - this released energy is ultimately used to synthesis a ATP - In oxidation, a substance loses electrons, or is oxidized - In reduction, a substance gains electrons, or is reduced (the amount of positive charge is reduced). - the electron donor is called reducing agent - The electron receptor is called oxidizing agent. The one accepting electron - some redox reactions do not transfer electrons but change the electron sharing in covalent bonds "Since we were able to define the components in a chemical reaction such as the reducing agent and oxidizing agent in order to form a product. Remember metabolism also produces energy as a result of the degradation of larger molecules into smaller molecules and energy also utilized to synthesize a large molecule from small molecules" - Energy is the capacity to cause change - energy exists in various forms, some of which can perform work - kinetic energy is associated with motion - Heat (thermal energy) is kinetic energy associated with random movement of atoms or molecules -Potential energy is energy that matter possesses because of its location or structure -Chemical energy is potential energy available for release in a chemical reaction - energy con be converted from one form to another *One form of energy is the conversion of light in order for an organism to exhibit bioluminescence  THE LAWS OF ENERGY TRANSFORMATION -Thermodynamics is the study ox energy transformations - an isolated system, such as that approximated by liquid in a thermos, is isolated from its surroundings. There's still transfer of heat that's conserved in that surrounding - In an open system, energy and matter can be transferred between the system and its surroundings - since we interact with environment, organisms are open systems S I In always exchange change of o energy well energy that as the would be exchange as is only contained there exchange if of er betwe , an matter , the exchange of is from surrounding energy just to the the inside outside The first law of thermodynamics: - According to the first law of thermodynamics, the energy of the universe is constant - energy can be transferred and transformed, but itO can't be created or destroyed - the first law is also called the principle of conservation of energy - you will have the same energy that will be taken in by body and energy that will be escalated out of body although in other form, would still be the same - The second law of thermodynamics: - During every energy transfer or transformation, some energy is unusable, and is often lost as heat - according to the second law of thermodynamics, every energy transfer or transformation increases the entropy (disorder) of the universe - In a bear that would eventually run in order for it to hunt for food, it would release that energy and at the same time some of the products of its metabolic activity would result to the excretion of carbon dioxide and some amount of water. - - - - biologists want to know which reactions occur spontaneously and which require input I of energy. - to do so, they need to determine energy changes that occur in chemical reactions Free-energy change G - A living system's free energy is energy that can do work when temperature and pressure are uniform, as in a living cell - there is a certain formula from which this free energy can actually be changed into one form into another - The concept of free energy can be applied to the chemistry of life's processes - an exergonic reaction proceeds with a net release of free energy and is spontaneous - an endergonic reaction absorbs free energy from its surroundings and is non- spontaneous - two types of chemicals reactions: endergonic and exergonic -requires absorption of free energy - endergonic has positive energy, exergonic has negative energy -Endergonic reactions require energy, exergonic releases energy - exergonic is spontaneous and endergronic is non-spontaneous - exergonic is spontaneous because it can occur without addition of energy - in exerganic, reactant has more energy than product - endergonic is non-spontaneous cuz it requires energy. Energy must be added before it can proceed - In endergonic, product has more energy than reactant, meaning it absorbs energy. - In photosynthesis, its endergonic. In order con photosynthesis to work, most absorb energy from sun to produce glucose and oxygen - In cellular respiration, its exergonic.it releases energy for cells to do its work cuz breaking of- carbon hydrogen covalent bonds within sugar is being released. Releases energy or releasing energy by breaking down glucose into smaller molecules EQUILIBRIUM AND METABOLISM - Reactions in a closed system eventually reach equilibrium and then do no work -Cells are not in equilibrium; they are open systems experiencing a constant flow of materials - A defining feature of0 life is that -0- metabolism is never at equilibrium - A catabolic pathway in a cell releases free energy in a series of reactions - Closed and open hydroelectric systems can serve as analogies - an example of a closed system that undergoes equilibrium and does no work *Reactions in a closed system eventually reach equilibrium and then do no work  *Cells are open systems experiencing a constant flow of materials open system - water still of same - level even if its of the diff. chumbers and will still predece that which is that energy light - Take note that in metabolism, we have these chemical reactions in order to produce a product. In order to produce product, it will require utilization of energy and this utilization or activation energy in order to produce a product, it requires an enzyme that would speed up this catabolic reaction and would later on lower these energy barriers Or would not consume much of the energy. - Enzymes speed up metabolic reactions by lowering energy barriers - a catalyst is a chemical agent that speeds up a reaction without boing consumed by the reaction - An enzyme is a catalytic protein - hydrolysis of sucrose by the enzyme suprase is an example of an enzyme-catalyzed reaction Here, is an example that would utilize ' the enzyme sucrase in order for sucrose to be degraded. Sucrose is a disaccharide. In order for it to be degraded into simple sugar glucose and fructose, it would require the utilization of an enzyme in order to break down this disaccharide into single sugar The activation energy barrier: - Every chemical reaction between molecules involves bond breaking and bond forming - the initial energy needed to start a chemical reaction is called free energy of activation or activation energy (EA) - activation energy is often supplied in the form of thermal energy that the reactant molecules absorb from their surroundings shows now activation - thered be O a energy is required in order for of ~ requirement a chemical reaction to accur order to EA in a produce product - Enzymes catalyze reactions by lowering the activation energy barrier 0 - enzymes do not affect the change in0 = free energy; instead, they hasten reactions that would occur eventually wo enzyme , would require - high EA. in order to procce a product with enzyme , - Et is lower  Shows how enzyme functions in order for a chemical reaction to occur and produce a product -Enzyme is substrate specific and can only accommodate a certain substrate that can attach to its active site -Here, we see the active site in which it can accommodate a specific substrate. - so once these substrates are held in the active site, this can now lower the activation energy and can now have a reaction producing a product - Subtrates are now converted into products and it will be released from active site of enzyme and now its available con another set of substrate molecules - this means the enzyme is not degraded? In this case  CELLULAR RESPIRATION - Respiration is the process that the body uses to release energy from digested food (glucose) - cells are busy doing processes all the time - many of the processes they do require ATP energy - ATP is a type of nucleic acid and has 3 phosphates - when chemical bond that holds that 3rd phosphate is broken, energy is released and is converted to ADP (adenosine diphosphate) -Cells need to make ATP energy. It doesn't matter which cell. Eukaryotes and prokaryotes have to make ATP, but process can be different depending on the type of cell - cellular respiration is pertaining to a process in which a body is able to release or synthesize energy bused on a larger molecule -It is different from respiration in which there would be an exchange of gas between an organism to its external environment or within the cell, to the different parts of the tissues - were talking about here, on how a larger molecule that would be broken down will be able to release energy - glucose composed of 6 molecules of carbohydrate which would later on be degraded in order for it to produce energy O What is the difference between cellular respiration and - CR is breathing (respiration)? Respiration (breathing) is the way your body gets oxygen into the lungs from the air outside. Cellular a form respiration describes how your cells make ATP - a molecule Of used to provide energy for chemical reactions metabolism I from food animals take in  MAJOR PLAYERS IN CELLULAR RESPIRATION Adenosine triphosphste (ATP): -Energy source for all cells. Considered the "energy currency" of the cell. 0 O Releases large amounts of energy when converted to adenosine diphosphate = (ADP) --energy currency of the cell because it is the one usually involved in all - catabolic and anabolic activity that can occur in a cell. Energy source for all activities that can be observed in a cell O - In ord'er to produce ATP, ADP should be phosphorelated first. When you say phosphorelated, there should be a presence of a phosphate in order for it to produce ATP. NAD+/NADH FAD/FADH2 3 respiration to create ATP E Energy intermediates. Used at the last stage of cellular  ATP-ADP CYCLE - Stands for adenosine triphosphate - Chemical compound used to stove and release energy in cells - Very important to all living organisms ATP ATPsynthase Atpase · energy · + t oxygen · water phosphate ADP 1. ATP is broken down into  Harvesting of energy from glucose has 3 stages - Glycolysis (breaks down glucose into 2 molecules of pyruvate) - the citric acid cycle (completes the breakdown of glucose) - oxidative phosphorylation ( accounts for most of the ATP synthesis) G require a trobic axygen. *In order for these 3 stages to all occur, a certain organism must undergo cellular respiration in the presence of oxygen Glycolysis will break down the glucose in to 2 pyrovate and with the presence of ' oxygen, these pyruvates will now enter citric amid cycle cuz this will lead to complete breakdown of glucose and then, with the presence of oxygen, it will undergo oxidative phosphorylation and on this stage, you will have more ATP synthesis that will observed - Oxidative phosphorylation accounts for almost 90% of the ATP generated by cellular respiration - A smaller amount of ATP is formed in glycolysis and the citric acid cycle by substrate -level phosphorylation *ATP produced by means of phosphorylation. When you say phosphorylation, for example, in the presence of an enzyme which is specific to a substrate, it is phosphorylated G in the presence of ADP. So from this reaction, the enzyme together with substrate, will produce a product and since phosphorylated, it will produce ATP. - A direct production of ATP is actually called substrate- level phosphorylation but smaller amount of ATP produced - oxidative phosphorylation. This is a form of phosphorylation or a synthesis of ATP where more ATP is produced -ATP is synthesized in mitochondria PHASES OF CELLULAR RESPIRATION: Glycolysis - Glycolysis (sugar splitting) breaks down glucose in to 2 molecules of pyruvate - glycolysis occurs in the cytoplasm and has two major phases: Energy investment phase energy pay off phase -Glycolysis occurs whether on not O2 is present - its called-energy investment phase because in order for glucose to be broken down, it - requires ATP to break down the 6 carbon sugar - In the# energy payoff, because of the breaking down of glucose, there would be, - phosphorylation, thus ATP will now be produced - glycolysis is anaerobic (does not require oxygen) can be aerobic - glycolysis occurs in the cytosol, cytoplasm of cell - the he word glycolysis means sugar splitting which is what exactly happens during the path way - If oxygen is present, then chemical energy stored in pyruvate and NADH can be extracted by the citric acid cycle  - During 1st phase, cell spends ATP, uses ATP that's why called energy investment but the investment is repaid with interest during energy pay off phase, when G ATP is produced by the- - phosphorylation and NAD+ is reduced to NADH- by electrons, released from the oxidation of the glucose 1. Glucose enters the cell and is phosphorylated -Phosphorylated (particularly dephosphorylation for atp-adp) meaning ATP to ADP, releasing one phosphate -Accompanied by the enzyme, hexokinase - enzyme catalyzes or assists the process - hexokinase produces glucose 6 phosphate - glucose gains energy by being phosphorylated at the expense of one ATP - The first step in glycolysis is catalyzed by hexokinase, an enzyme with broad specificity that catalyzes the phosphorylation of six-carbon sugars. Hexokinase phosphorylates glucose using ATP as the source of the phosphate, producing glucose-6- phosphate, a more reactive form of glucose 2. G6P converted into F6P - F6P is known as fructose 6 phosphate  - will be converted to F6P with the presence of Phosphoglucoisomerase enzyme 3. With phosphate group at apposite ends, the sugar is now ready to split in half - Will produce fructose 1, 6- biphosphate (F1, 6-BP) and then ready to split in half - this occurs with the presence of phosphofructokinase - another ATP utilized end phosphanylation 4. The 6 enzyme cleaves the sugar molecule into 3-carbon sugars: DHAP and G3P - The enzymeE aldolase will cleave or produceO 2 three-carbon sugars being dihydroxyacetone phosphate (DHAP) and - glyceraldehyde 3-phosphate (G3P) 5. When this happens, the enzyme isomerse, will now catalyze the reversible convers'ion between theG 2 three-carbon sugar G - all DHAP converted toG G3P - *2 ATP used in energy investment phase 6. The sugar is oxidized by the transfer of electrons and H+ to NAD+, forming NADH - NAD+ will be converted to NADH through the help of trios phosphate dehydronase (enzyme). - after step 6, BPG is created - BPG: 1,3-biphosphoglycerate 63P - -2 NADH produced 7. Glucose has been converted to 2 molecules ofO 3PG -BPG converted to 3PG through help of phosphoglycerokinase '" -3PG: 3-phosphoglycerate and 2 ATP produced from 2 ADP 8. The enzyme relocated the remaining phosphate group, preparing the substrate for next reaction - enzyme: phosphoglyceromutase - Converted to 2PG or 2- phosphoglycerate to undergo the following action 9. The enzyme enolase causes a double bond to form in a substrate by extracting water molecule, yielding PEP - Extaction of water (H2O) - PEP: phosphoenolpyruvate 10. Glycolysis produces more ATP by transferring the phosphate group from PEP to ADP - Assisted by enzyme: pyruvate kinase - end product: 2 pyruvate - 2 ADP to 2 ATP -2 Cu26 glucose divided into 2 3 carbon sug Products of glycolysis: - 2 NADH - 4 ATP  THE FATE OF PYRUVATE: - In the presence of oxygen, pyruvate enters the mitochondrion (in eukaryotic cells) where the oxidation of glucose is completed - before the citric acid cycle can begin, pyruvate must be converted to acetyl Coenzyme A (acetyl CoA), which links glycolysis to the citric acid cycle. This happens before oxidation or entering mitochondrion O ⑧ - - 1 CO2 and 2 NADH molecule formed when converting pyruvate to acetyl CoA - it no oxygen, pyruvate will be processed by means of fermentation and product is in the form of ethanol, lactate or other products -For anaerobic, it would produce products such as ethanol or alcohol or lactate - aerobic oxidation, pyruvate converted to acetyl CoA and enter citric acid cycle and I oxidative phosphorylation  - Fermentation in anaerobic respiration ennobles cells to produce ATP without use of oxygen because it exhibits a substrate level of phosphorylation - without O2, the electron transport chain will cease to operate -In that case, glycolysis couples with anaerobic respiration or fermentation to produce ATP but with smaller amount and other products - anaerobic respiration uses an electron transport chain with a final electronG Oacceptor other than oxygen, for example sulfate to generate ATP - fermentation uses substrate-level phosphorylation instead of an electron transport chain to generate ATP. For fermentation usually the product is in the form of organic substances Substrate-level phosphorylation occurs in the cytoplasm of cells (glycolysis) and in the mitochondria (Krebs cycle). It can occur under both aerobic and anaerobic conditions and provides a quicker, but less efficient source of ATP compared to oxidative phosphorylation. Both inorganic and organic compounds may be used as electron acceptors in anaerobic respiration. Inorganic compounds include sulfate (SO42-), nitrate (NO3–), and ferric iron (Fe3+). Organic compounds include DMSO. These molecules have a lower reduction potential than oxygen. Therefore, less energy is formed per molecule of glucose in anaerobic versus aerobic conditions. The reduction of certain inorganic compounds by anaerobic microbes is often ecologically significant. Citric acid cycle (kreb's cycle): - Also known as tricarboxylic acid (TCA) cycle - can O only occur in presence of oxygen or thru aerobic respiration - Occurs inside mitochondria - must be converted to acetyl CoA first - The citric acid cycle has 8 steps, each catalyzed by a specific enzyme - The NADH and FADH2 produced by the cycle relay electrons extracted from food to the electron transport chain - the pyro vale made before is converted and will be oxidized. - 2 CO2, 2 ATP molecules, 6 NADH and 2 FADH2 produced Stotal with 2 - In the conversion of pynuvate to acetyl CoA, each pyrvvalle molecule cases pyruvate one carbon atom with the release of CO2 - electrons are also transferred to NAD+ to produce NADH which will used by cell to produce ATP - matrix of mitochondrion and cytosol for prokaryates - produces citric acid which has 6 carbon atoms - One pyruvate = one acetyl CoA so multiply products by 2 ↑ Refer to written notes Oxidative phosphorylation: - following glycolysis and the citric acid cycle, NADH and FADH2 account for most of the - energy extracted from food ~ from t and Kreb - these 2 electron carriers dance electrons to the electron transport chain, which powers ATP synthesis via oxidative phosphorylation -Type of phosphorylation where more ATP is produced as compared to substrate level phosphorylation - subtrate - level cours in cytoplasm -Oxidative phosphorylation occurs in the inner membrane of mitochondrion O 8 V & Atp produce more Electron transport chain - this is known as electron transport chain because there would be movement of electrons from one protein molecule into another protein molecule - The NADH produced from glycolysis and Karen, will pass through in one of the molecules embedded in the inner membrane of the mitochondrion - and once passes one molecule, it will produce hydrogen electrons from outer membrane and pass thro another molecule and produce another n'inete cube roger and another one so water is produced - The hydrogen produced will enter cell by means of ATP synthase and this will now be phosphorylated and produce ATP O - For NADH, 3 molecules ofO there will beG ATP that would be produced -OFADH2 is imonedichely process through this protein molecule number 2 and would pass through one molecule and② release oxygen and then another molecule and release oxygen so that means forO FADH2, it wil produceO2 ATP NADH = 3 ATP FADH2 = 2 ATP i - - - - - -  total ATO can differ cut there would based protein component - on differences in the species be that is present in mumbrane , not rein same embeced in mitoch dieites - can we catabolize other macromolecules other than glucose? Yes like proteins and fats - proteins are digested to amino acids; amino groups can feed glycolysis or the citric acid cycle -Fats are digested to glycerol (used in glycolysis) and fatty acids (used in generating aceetyl CoA) of I cut glycolysis  CELL CYCLE - It includes the cell division process - cell division: cell divides to increase in number and grow and produce daughter cells that will participate in fertilization called gametes - cell division is the ability of organisms to produce more of their own kind best distinguishes living things from non-living matter - the continuity of life is based on the reproduction of cells or cell division - It is categorized into 2 types: mitosis land meiosis - one of the property of living organismis reproduction and this can be seen in unicellular and multicellular organism - In unicellular organisms, division of one cell reproduces the entire organism - exactly same as parent cell for unicellular - clone of parent Amoeba - Multicellular eukaryotes depend on cell division for - 2 Development from a fertilized egg nucleus repair of cells or tissues growth Division also differs depending it its sexual or asexual Fertilized cell , mitosis -Cell division is an integral part of the cell cycle, the life of a cell from formation to its own division - cell division involved in tissue renewal and cell division is a part of that cull cycle in which a cell does not only divide, it also grows. That means that its just a small part of that entire growth phase of a cell  - Most cell division results in daughter cells with identical genetic information, DNA - there are two types of cell division: mitosis and meiosis - the exception is meiosis, a special type of division that con produce sperm and egg cells - Mitosis only occurs among somatic cells while meiosis occurs among germ cells - somatic cells are body cells -Germ cells are sperm and egg cell -In mitosis, parent cells will produce 2 daughter cells that would have same amount of chromosomes as of the parent so for example, it parent is diploid, then 2 daughter cells would also have thee diploid number of cells. Same amount of chromosome or DNA as of the parent -In meiosis, produce 4 daughter cells that would contain half of the amount of chromosomes as compared to the parent - only one phase of mitosis, 2 phases for meiosis -daughter cells have same genetic information for mitosis. Since haploid for meiosis, only half number of chromosomes of a parent. Half mother and half of father Both unicellular and multi undergo mitosis - all the DNA in a cell constitutes the cell's genome - since were talking about genetic material that would be transferred from parents to offspring, take note that this genes that are being reflected in an organism is because it is part of that segment of that DNA in which all cells have - a genome can consist of a single DNA molecule (common in prokaryotic cells) or a number ox DNA molecules (common in eukaryotic cells) - DNA molecules in a cell are packaged into chromosomes - genome is a number DNA molecules that would produce a trait - Chromosome is a condensed form of a DNA molecule and is a term utilized if cell is undergoing cell division. If cell not undergoing cell division, then we call the genetic material chromatin (undergoing CD) - chromosome - Eukaryotic chromosomes consists of chromatin, a complex of DNA and protein that condenses during cell division - there's protein cuz in order for a long strand of DNA to fit in small cell size, it has to undergo this coiling of the long DNA (DNA of eukaryote is linear) and this coiling is caused by the presence of the protein. Chromosome when condenses during CD - every eukaryotic species has a characteristic number of chromosomes in each cell nucleus - Somatic cells (non-reproductive cells) have 2 sets of chromosomes -gametes (reproductive cells: sperm and egg) have half as many chromosomes as so somatic cells Distribution of chromosomes during eukarytorc cell division - In preparation for cell division, DNA is replicated and the chromosomes condense - each duplicated chromosome has 2 sister chromatids (joined copies of the original chromosome), attached along their lengths by cohesions - the centromere is the narrow "waist" of the duplicated chromosome, where the 2 chromatids are most closely attached - The 2 sister chromatids joined by centromere and centromere is important cuz it will guide the chromatids during its movement in the cytoplasm in cell division - the spindle fiber would hold the centromere and then will help in separation of these 2 sister chromatids during cell division -During cell division, the 2 sister chromatids of each duplicate chromosome separate and move into 2 nuclei -once separate, the chromatids are called chromosomes -eukaryotic cell division consists of: mitosis, the division of the genetic material in the nucleus cytokinesis, the division of the cytoplasm and reflected by the presence of a cleavage furrow -Gametes are produced by a variation of cell division called meiosis - meiosis yields non-identical daughter cells that have half as many chromosomes as the parent cell - Mitosis has two divisions. Division of nucleus and division of cytoplasm - division of nucleus is called karyokinesis and is the time between when the cell is undergoing prophase until early stage of telophase - Mitosis, like clone of parent, exact same. A skin cell will produce a skin cell and same with muscle cell. But for meiosis, it would lead to variation of cell or organism because contains genetic material of 2 individuals  Chromosome - organized package of DNA found in the nucleus of the cell E - thread-like structures - each chromosome is made up of DNA tightly coiled many times around proteins called histones that support its structure Sister chromatids - pairs of identical copies of DNA joined at a paint called centromere - during anaphase, each pair of chromosomes is separated into 2 identical independent chromosomes - formed by replication of a chromosome during s-phase Daughter chromosome -Is a chromosome that results from the separation of sister chromatids during cell division O-anaphase - sister chromatids become daughter chromosomes (telophase) Centromere ?? -Constricted region of a chromosome that separates it into short and long arm -Provide foundation for assembly of kinetochore - attachment of sister chromatids and site for attachment of spindle fibers and help in proper alignment and segregation of the chromosomes during cell division in eukaryotic cells Kinetachore - Disc-shaped protein structure associated with duplicated chromatids in eukaryotic cells where spindle fibers attach during cell division to pull sister chromatids apart - help during cell division by making sure that each new cell has one chromatic from each pair - no kinetochane? Resulting cells would be missing a chromosome  Spindle fibers - Are filaments that form mitotic spindle in cell division ie. Mitosis, meiosis ②-Chiefly involved in moving and segregating chromosomes during nuclear - - division (cell division is process of splitting parent cell into a daughter cells, nuclear division is process of obtaining 2 daughter nuclei by splitting parent nucleus) -Spindle diner made of microtubules -Microscopic protein structures that help divide genetic material during cell division and organize cellular components - Form out of centrosome Gametes - haploid sex cells that contain 1 copy of chromosome - sperm and egg Somatic cells - Growth, repair, generation - any cell extent reproductive cells (egg and sperm) - ex.: nerve cells, skin cell, blood cells - all cells of body except gametes - also known as body cells -From ancient Greek word "soma" which means body Diploid - 2 sets of chromosomes (one from each parent) - diploid cell has 46 chromosomes 23 Haploid -pain hamolo of & chromosomes diploid in - has 2 copies of homologous chromosomes in nucleus parent cell -Homologous chromosomes are pair of chromosomes that contain the same gene derived Leach sequence fromparent a - cells other than sex cells have 23 pairs of chromosomes so 46 chromosomes total Mitotic spindle - The mitatic spindle is a structure made of microtubules that controls chromosome movement during mitosis - In animal cell, assembly of spindle microtubules begins in the centrosome, the microtubule organizing center -Microtubules one of the cytoskeleton that's involved in division - centrosome made up of two microtubule-based centrioles - The centrosome replicates during interphase, forming 2 centrosomes that migrate to apposite ends of the cell during prophase and prometaphase - The spindle includes the centrosomes, the spindle microtubules and the asters Aster - an aster (a radial array of short microtubules) extends from each centrism Kinetochores - Kinetochores are protein complexes associated with centromeres - during prometanshase, some spindle microtubules attach to the kinetochores of chromosomes and begin to move the chromosomes Metaphase plate - At metaphase, the chromosomes ave all lined up at the metaphase plate, a plane midway between the spindles 2 poles - imaginary plate  How microtubules help in the movement of the chromosome during cell division? - InEanaphase, the cohesins are cleaved by an enzyme called separase - Sister chromatids separate and move along the kinetochore microtubules toward opposite ends of the cell - microtubules shorten by depolymerizing at their kinetochore ends & microtubule attach to kine Rechare Cleavage furrow - In animal cells, cytokinesis occurs by a process known as cleavage, forming a cleavage furrow - cleavage is one of the stages in the early development of an animal - image using scanning electron microscope  Cell Cycle Control - The eukaryotic cell cycle is regulated by a molecular control system - The frequency of cell division varies with the type of cell - these differences result from regulation at the molecular level - cancer cells manage to escape the usual controls on the cell cycle. They escape check points in cell cycle - The sequential events of the cell cycle are directed by a distinct cell cycle control system, which is similar to a clock oc - the cell cycle control system is regulated by both internal and external controls oc - the clock has specific checkpoints where the cull cycle stops until a go-ahead signal is received Checkpoint has like 9 Steward gasignal - This will determine it there will be fault in a certain cell. And it there is, it will not loud to its division and will undergo apoptosis or moved out of cycle and enter G0 - for many cells, the G1 checkpoint seems to be the most important - - if a cell cell receives a go-ahead signal at G1 checkpoint, it will usually complete the S, G2 and M phases and divide. - if the cell does not receive go-ahead signal it will exit cycle, switching into a non- dividing state called the G0 phase.  Taurind mitosis Cancer: - Cancer cells do not respond normally to the body's control mechanisms - it does not recognize checkpoints - cancer cells is actually the result of once it is in the G0 state, it will renter the cell cycle and it will continuously divide. That's why Carmen culls are metastasizing growing (means abnormally in #) - A normal cell is converted to a cancerous cell by a process called transformation -Cancer cells that are not eliminated by the immune system form tumors, masses of abnormal cells within otherwise normal tissue - If abnormal cells remain only at the origina site, the lump is called benign tumor - Malignant tumors invade surrounding tissues and can metastasize, exporting cancer cells to other parts of the body, where they may form additiona tumors - localized tumors may be treated with high-energy radiation, which damages the DNA in the cancer cells - to treat metastatic cancers, chemotheraptes that target the cell cycle that lead to the increase of these cancer cells may be used - however, chemotheraptes can affect normal cells. That's why these people feel work since normal cells affected  Asexual reproduction - type of reproduction that requires one parent to produce daughter cell - no fusion at gametes or change in number of chromosomes all throughout The cell cycle - The cell cycle consists of (2 major phases) Mitotic (M) phase (mitosis and cytokinesis) interphase (cell growth and copying of chromosomes in preparation for & cell grow first 34 divide cell division) - Interphase (about 90% of the cell cycle) can be divided into subphases G1 phase (first gap) duplication organelles - of synthesis S phase ("synthesis") DNA - G2 phase ("second gap") prepare cato the - - The cell grows during all three phases but chromosomes are duplicated only during S phase - Difference between dividing and non-dividing cell is the genetic material within nucleus alrea - visible Intact nuclear · Degraded nuclear membrane, intact membrane/envelope, thus, genetic material is nucleolus, chromatin already in cytoplasm, chromosomes Interphase: - cell being prepared for division in preparation for mitotic phase or cell division - cell growth -longest phase - DNA replication - consists of substages - don't have cell division, but growth instead -Most cells live here - Period where cells spend most of their time - exemption: cancer. Cancer cells have a defect that cause them to divide more than grow G1 Phase - increases in size - organelles are built - protein synthesis - prepares for DNA replication - enter here after completing cell division or m-phase - towards end of phase, cell must be sufficiently healthy to replicate DNA -Can proceed to s-phase if undamaged and enough growth factors or resources quailable for cell to keep growing - from here, cell has a choice to continue growing and moving towards direction of cell division - It call is damaged and irreparable or resources are insufficient, cell enter G0 phase knowm as resting or non- dividing phase or cell can die from damage -Apoptosis: form of programmed cell death or cellular suicide - however, cells also undergo apoptosis to make way for new cells. Apoptosis is also a defense against damaged or dangerous cells and can maintain balance of a cell in human body and is particularly important in immune system - apoptosis is different from necrosis -Necrosis: process wherein cell die due to injury - apoptosis: cell self-destruct it self due to insufficient nutrients or resources in their development -If lack growth factor or nutrients and instead af undergoing apoptosis, call can enter resting state (G0) -Cell can leave G0 - cell can exit cell cycle if it receives a signal to differentiate or resources are insufficient - cell diffrrenciation is known when cells become specialized cells or cell differeciation may simply be described as the process thru which a young immature mess evolves into a specialized all. Differentiation cells are important in multicellular organisms cuz they perform specialized functions, in the body. However, specialized carne's at a cost which is that differentiated cells after lose the ability to make copies ox themselves. Only some cells may divide again but there are certain conditions. The rest fo to G0 - neverons and muscle cells are in G0 -cells can remain in G0 and never renter cycle - neurons permanently blocked from cell cycle once differentiated - Liver injury causes cells to leave G0 G1 Checkpoint - check cell size, is cell large enough for cell division? -Check cell nutrients, does the cell have enough reserve energy and nutrients or resources con cell division? -DNA integrity and molecular signals, does cell receive growth factors and other signals from neighboring cells? - towards end of G1, cell has to be sufficiently healthy to replicate its DNA -It DNA damaged and not enough resources available to divide and grow, it will go to G0 or apoptosis if irreparable - if met requirements, growth signals stimulate for proceeding to s-phase  S-Phase - S stands for synthesis (specifically DNA synthesis) - DNA replication O -23 pairs of chromosomes and replicate them and result to 46 pairs (92 - chromosomes) - most cells go in this direction but Can go to G0 or Gnut where no more cell division cuz some cells in body don't tend to divide like neurons in brain. when brain formed, no need to divide anymore. Neurons wont go back and enter cycle 06 - Longest and most essential stage of interphase cuz of complexity of replication of generic materials = -Cell complete chromosomes - each of 46 chromosomes are duplicated by cell - No error in replication, growth signal will stimulate cell to proceed to G2 S-Phase Checkpoint - Checks for DNA errors - DNA continuously monitored for replication error in s-phase - if no error, growth signals stimulate to proceed to G2  G2 Phase - Growth phase - More directly preparing for mitosis - by making michotubules which will be used to pull chromatids apart when it comes time for anaphase - final phase of interphase where cell prepares itself con cel division process - further development of ordered growth and final preparation of the cell - ensures DNA replication is complete -All enrumosumes have to be fully replicated and no damage in dudes le enter m-phase and device G2 Checkpoint - DNA integrity, is any port of DNA damaged? - DNA replication, is DNA replication completed in s-phase on are chromosomes set complete? -It there's an Enron, cell will pause in G2 and allow some time to repair itself - DNA no damage -Enough cell components - no error, proceed to m-phase M Checkpoint - Also known as metaphase checkpoint or spindle checkpoint - all sister chromatids attached to mitotic spindle - If all chromosomes attached to spindle fibers and alignment at m-plate - without full chromosome attachment, stop signal received - During mitosis  Stages of mitosis Prophase/Prometaphase - Chromosomes condenses and become visible - Nucleolus disappears - nuclear envelope breaks down (fragments) -Spindle starts to form between centrioles - chromatin condenses into chromosomes - Spindle invades the nuclear area, some microtubules attoch to kinetochare -DNA coils very tightly shortening and thickening chromosomes - protein called microtubules assemble into spindle between 2 centrosomes and help separate replicated chromosomes into daughter cells -n prophase, the nucleolus disappears and chromosomes condense and become visible. In prometaphase, kinetochores appear at the centromeres and mitotic spindle or Metaphase microtubules attach to kinetochores. - -In prophase of mitosis, specialized regions on centromeres called kinetochores attach chromosomes to spindle fibers. The centromere is the part of a chromosome that links sister chromatids. During mitosis, spindle fibers attach to the centromere via the kinetochore. here use /Metaphase ?? Metaphase - Chromosomes (arranged in pairs) line up in middle of the cell and nucleus disappears - chromosome align at metaphase plate - Nucleolus disappeared - Nuclear envelope disappeared - Spindle toggles the chromosomes towards the equator - mitosis spindle fully developed and attached to the centromeres of each chromosome, specifically kinetochore - the arrangement ensures each cell will receive due dt each chromosome Anaphase - Chromatids separate and more towards the pales ox the cell - Nucleolus splits into 2 - Nuclear envelope, they form around chromosomes and nucleosomes - spindle shorten and pull sister chromatids towards spindle poles -Separation of chromosomes away from metaphase plate - movement of each chromatid towards opposite poles - centromere splits Telophase - Chromosomes arrive at apposite sides of the cell - nucleolus enlarge and reappear - Surrounds each set ot chromosomes, reappear -Spindle disappears -Pulled chromosome reach the 2 ends of a cell -Start of cytokinesis: total separation - cytokinesis: division of cytoplasm, formation of 2 identical daughter cells (main event) - nuclear envelope reintegrates - chromosome uncoils - become less distinct - once chromosome reaches end of cell, cytokinesis starts - for animal cytokinesis, cleavage furrow formed. And cell plate for plants - nuclear envelope and nucleolus form at each end ox stretched out cell - as telophase ends, division of genetic material is compute and cell contains 2 nuclei - first sign of cytokinesis in animals is an indentation called cleavage turn milosis identical to - , starring cell Karyokinesis occurs before cytokinesis , telaphase ? Additional notes! The main difference between telophase and cytokinesis is that telophase is the final step of karyokinesis, which forms two daughter nuclei. Meanwhile, cytokinesis is the final step of cell division, equally distributing cytoplasm between the two daughter nuclei - Cytokinesis begins in anaphase and ends in telophase, Lincab reaching completion as the next interphase begins. The first visible change of cytokinesis in an animal cell is the sudden appearance of a pucker, or cleavage furrow, on the cell surface. , occurs says Test as  Meiosis -Living organisms are distinguished by their ability to reproduce their own kind - heredity is the transmission of traits from one generation to the next - variation is demonstrated by differences in appearance that offspring show from parents and siblings - genetics is the specific study of heredity, genes and variation - meiosis leads to variation of individuals.it is because there would be a mixture of traits between the parents - genes are the unity ox heredity and are made up of segments of DNA - genes are passed to the next generation via reproductive cells called gametes (sperm and egg) - most DNA is packaged into chromosomes - humans have 46 chromosomes in their somatic cells, all cells ox the body except gametes, and their precursors O - A gene's specific position along a chromosome is called the locus. Site where it will crosslink with homologous chromosome during meiosis Asexual and sexual reproduction - In asexual reproduction, a single individual passes all of its genes to its offspring without fusion of gametes ~ leads to clone - A clone is a group of genetically identical individuals from the same parent - In sexual reproduction, 2 parents give rise to offspring that hole unique combinations ot genes inherited from the two parents leads to variation -  karyotyping - - Human somatic cells hove 23 pairs of chromosomes (46 chromosomes) - A karyotype is an ordered display of the pairs of chromosomes from a cell - the 2 chromosomes in each pair are called homologous chromosomes or homologs WeO - chromosomes in a homologous pair are the same set romosome length and shape and carry genes controlling the. 2 are somatic chromosomes same inherited characters - x and y is male, x and x is female M1 starts wirh - karyotyping is important so we can determine one diploid naient any abnormality in an organism. Will let us know if there was be an excess chromosome and or less chromosome or faulty part of ends with 2 chromosome -When you say faulty, the chromosome would haploid. have shorter form as compared to a regular With one. This will lead to a condition which Bo fatal M2 starts 2 haphore with or not. - chromosome number 1 of male will pair with dends Med number 1 chromosome of female (homologous chromosome) - - must be 1 to 1.has to have same trait to be mixed traits, I to I want produce the it hd produce - each pair of homologous chromosomes includes one chromosome from each parent - The 46 chromosomes in a human somatic cell are 2 sets of 23: one from mother and one from father - A diploid cell (2n) has 2 sets of chromosomes - for humans, the diploid number is 46 (2n=46) - once fertilization occurs, starts as a diploid - since will enter meiosis, diploid will become haploid - A gamete contains a single set of chromosomes and is haploid (n) - for humans, the haploid number is 23 (n=23) - each set of 23 consists of 22 autosomes and a single sex chromosome -In an unfertilized egg (ovum), the sex chromosome is x -In a sperm cell, the sex chromosome may be x or y -Fertilization is the union of gametes - the fertilized egg is called zygote and has one set of chromosomes from each parent - the zygote produces somatic cells by mitosis and develops into an adult  - Like mitosis, meiosis is preceded by the replication of chromosomes - meiosis takes places in a consecutive cell divisions, called meiosis 1 and meiosis 2 - The 2 cell divisions result in 4 daughter cells, rather than 2 daughter cells in mitosis - each daughter cull has only half as many chromosomes as the parent cell - Meiosis 1 start with diploid and end with haploid. - Meiosis 2 is same as mitosis -Meiosis II resembles mitosis, with one sister chromatid from each chromosome separating to produce two daughter cells. Because Meiosis II, like mitosis, results in the segregation of sister chromatids, Meiosis II is called an equational division. -Meiosis 1 starts with union of homologous chromosomes - prophase is one of most important part of meiosis cus the homologous Chiasmata are sites of crossover chromosomes are crossing over where in there will the exchange of genetic material between the two parents  MENDELIAN GENETICS What principles account for the passing of traits from parents to offspring? - The blending hypothesis is the idea that genetic material from the 2 parents blends together (like blue and yellow paint blend to make green) - The particulate hypothesis is the idea that parents pass on discrete heritable units (genes). - Mendel documented a particulate mechanism through his experiments with garden peas. Gregor Mendel is considered to be the father of genetics. Mende discovered the bas'ic principles of heredity by breeding garden peas in carefully planned experiments. Character: heritable feature that varies among individual (such as flower color or shape) Trait: each variant for a character, such as purple or white color for flowers, wrinkled or round for shape Other advantages of using peas: - short generation time so he can eventually see the results - large numbers of offspring - mating could be controlled (plants could be allowed to self-pollinate or could be cross pollinated)  In order to study heredity, Mendel mated two contrasting, true-breeding varieties, a process called hybridization - The true-breeding parents are the p-generation (P stands for parents) - The hybrid offspring of the p-generation are called f1 generation - when F1 individuals selt-pollinate or cross-pollinate with other F1 hybrids, the F2 - - generation is produced. The offspring of F1. THE LAW OF SEGREGATION (MENDEL EXPERIMENT) - When Mendel crossed contrasting, true-breeding white and purple-flowered pea plants, all of the F1 hybrids were purple. Means purple here is a dominant trait -When Mendel crossed the F1 hybrids, many of the f2 plants had purple flowers, but some had white a ratio of about three to one, purple to white flowers, in the f2 generation - Only the purple flower factor was affecting flower color in the f1 hybrids Purple flower color is a dominant trait and the while flower is a recessive trait - The factor for white flowers was not diluted or destroyedE because it reappeared in the F2 generation. Mendel's law of segregation “During the formation of states that the alleles of an gamete, each gene separates individual, separate during from each other so that each the formation of gametes. gamete carries only one allele for each gene.” The law of segregation states that each individual that is a diploid has a pair When an organism makes of alleles (copy) for a gametes, each gamete particular trait. Each parent receives just one gene copy, passes an allele at random which is selected randomly. to their offspring resulting in This is known as the law of a diploid organism. The allele segregation. that contains the dominant trait determines the phenotype of the offspring. - Mendel observed the same pattern of inheritance in 6 other pea plant character (these include seed color, seed shape, pod shape, pod color, flower position and stem length), each represented by 2 traits - When Mendel called "heritable factor" which can be transferred from parents to offspring is now what we call as a gene - In order for us to understand how traits are being transferred from parent to offspring, we utilize a punnet square Punnet square: can show possible combinations of sperm and egg. A punnet square ' can show possible combinations of how this sperm and egg can be utilized in order for us to understand how traits can the transferred - capital letter represents a dominant allele HM - lowercase letter represents a recessive allele Homozygous: an organism with 2 identical alleles for a character HT Heterozygous: an organism that has 2 different alleles for the gene controlling that character -Here (red), since we have 2 capital letters, or 2 dominant alleles, which is represented by the same capital letter, therefore this is a homozygous purple flower - an example of HT would be this allele (blue) in which it is represented by both a capital and small letter. However, this is still purple because it exhibits the dominant trait color but the allele for the recessive, which is white is still obtained by offspring so therefore, this is heterozygous purple An organism's traits do not always reveal its genetic composition due to the different effects of dominant and recessive alleles. This is pertaining to the homozygous and heterozygous like for example, the heterozygous purple, although it has allele of recessive, what is reflected is the dominant trait which is purple Phenotype: physical appearance in which the dominant trait is reflected in an organism Genotype: genetic make up or looking at the allele that composes the organism Example: flower color in pea plants HM HT - PP and Pp plants have the same phenotype (purple) but different genotypes  The Testcross - A dominant phenotype could be either homozygous dominant or heterozygous - If any offspring displays recessive phenotype, the mystery parent must be - heterozygous so this can be obtained by using the punnet square and that is by means of a test cross - - monohybrid cross is a cross between heterozygotes following one character like for example if were just utilizing the flower color in order for us to understand how this trait can be displayed by the offspring, we will just use monohybrid. one character THE LAW OF INDEPENDENT ASSORTMENT - Developed by Mendel using dihybrid cross (following 2 characters at the same time) - it states that each pair of alleles (using dihybrid cross) segregates independently of each other pair of alleles during gamete formation - applies only to genes on different, non-homologous chromosomes or those far apart on the same chromosome - genes located near each other on the same chromosome tend to be inherited together  Crossing 2 true-breeding parents differing in 2 characters. Each character would assort independently of each other. - Produces dihybrids in the F1 generation - heterozygous for both characters dihybrid of yela Dihybrid cross (cross between F1 dihybrids) - Can determine whether 2 characters are transmitted to offspring as a package or independently Inheritance patterns are often more complex than predicted by simple Mendelian genetics - The relationship between genotype and phenotype is rarely as simple as in the pea plant characters - many heritable characterso O are not determined by only one gene with 2 alleles -However, the basic principles of segregation and independent assortment apply even to more complex patterns of inheritance Complete dominance: occurs when phenotypes of the heterozygote and dominant homozygote are identical Incomplete dominance: the phenotype of F1 hybrids is O somewhere between the phenotypes of the 2 parental varieties Codominance: 2 dominant alleles affect the phenotype in separate, distinguishable ways. An example of this would be the blood type in which there would be 2 In complete dominance, only one allele in the genotype is seen in the phenotype. In alleles in one blood type codominance, both alleles in the genotype are seen in the phenotype. In incomplete dominance, a mixture of the alleles in the genotype is seen in the phenotype.  The relation between dominance and phenotype ⑳ - A dominant allele does not subdue a recessive allele; alleles don't interact that way - alleles are simply variations in a gene's nucleotide sequence - for any character, dominance/recessiveness relationships of alleles depend on the level at which we examine the phenotype Frequency of dominant alleles - Dominant alleles areo alleles 0 not necessarily more common in populations than recessive -Ex: one baby out of 400 in the United States is barn with extra fingers or toes - The allele for this unusual trait is dominant to the allele for the move common trait of 5 digits per appendage - In this example, the recessive allele is far more prevalent Han the population's dominant allele Multiple alleles - Most genes exist in populations in more than two allelic forms - Ex: the four phenotypes of the ABO blood group in humans are determined by 3 alleles  Pleiotropy occurs when one gene influences two or more seemingly unrelated phenotypic traits. Pleiotropy - most genes have multiple phenotypic effects, a property called pleiotropy - Ex: sickle cell disease In homozygous individuals, all hemoglobin is abnormal = symptoms include physical weakness, pain, organ damage, paralysis heterozygotes are usually healthy but may suffer same symptoms = heterozygotes are less susceptible to the malarias parasite (an advantage) *Sickle cell disease is when the red blood cells don't exhibit a biconcave shape. - SCD ~ biconcave shape - Some traits may be determined by 2 or more genes m. An example of this is epistasis - In epistasis, a gene at one locus alters the phenotypic expression of a gene at a second locus - one gene determines the pigment color (with alleles B for black and b for brown) - the other gene (with alleles E for color and e far no color) determines whether the pigment will be deposited in the hair Epistasis. an allele of one gene modifies or prevents the expression of alleles at another gene.  Polygenic Inheritance - An additive effect of 2 or more genes on a single phenotype is being transferred from parents to offspring - skin color in humans is an example of polygenic inheritance. There would be variation. height asso A Mendelian view of heredity and variation -An organism's phenotype includes its physical appearance, internal anatomy, physiology and behavior - an organism's phenotype reflects its overall genotype and unique environmental history - many human traits follow Mendelian patterns of inheritance - this discovery of Mendel would really have a great contribution in the study of genetics Pedigree analysis - A pedigree is a family tree that describes the inter-relationships of parents and children across generations - inheritance patterns of particular traits can be traced and described using pedigrees -Pedigrees can also be used to make predictions about future offspring  Take note that during the time of Mendel, he utilized the plant but if we are using humans or some animals, the experiment would be unethical so in place of breeding experiments, genetisis will analyze the result of human mating by means of this pedigree analysis Recessively inherited disorders - many genetic disorders are inherited in a recessive manner - Range from relatively mild to life-threatening - show up only in individuals- homozygous for the allele - carriers are heterozygous individuals who carry the recessive allele but are phonetypically normal - albinism is a recessive condition characterized by a lack of pigmentation in skin and hair and this albinism can result to susceptibility to skin cancer and vision problems - cystic fibrosis is another example that can be life- threatening. Here, there is a problem in terms of the liver Dominant inherited disorders - although many harmful alleles are recessive, some disorders are due to dominant alleles - some human disorders are caused by dominant alleles - dominant alleles that cause a lethal disease are rare and arise by mutation - Achondroplasia is a form of dwarfism caused by a rare dominant allele Multifactorial disorders - Many diseases, such as heart disease, diabetes, alcoholism, mental illnesses, and cancer have both genetic and environmental components - No matter what our genotype, our lifestyle has a tremendous effect on phenotype -Many more people are also susceptible to diseases that would have multifactarial basis -When you say multifactorial basis, a genetic component would have also an effect together with its environmental influence  CHROMOSOME BASIS OF INHERITANCE Locating genes along chromosomes - mendel's "hereditary factors" were purely abstract when first proposed - today we can show that the factors are in the form of genes and are located on chromosomes - The location of a particular gene can be seen by tagging isolated chromosomes with a fluorescent dye that highlights the gene of interest - biologists began to see parallels between the behavior of mendel's proposed hereditary factors and chromosomes Here is an example of how genes are located on the chromosome. In diploid cells, the chromosomes and genes are present in pairs Chromosomes duplicate before cell division and each duplicated chromosome would have 2 copies of each allele. One on each sister chromatid During meiosis 1, homologous chromosomes separate and the alleles segregate In meiosis 2, sister chromatids separate. Genes are then on passed as discrete units and each chromosome would have one version of a gene and that would be 1 allele - The first solid evidence associating a sp'ecific gene with q specific chromosome came in the early 20th century from the work of Thomas Hunt Morgan. Morgan actually utilized fruit flies which is scientifically known as the drosophila melanogaster which is a common insects that feeds on the fungi which grows on the fruit. -Fruit flies are actually prolific breeders and a single mating can already produce hudreds of offsprings. Thus, for Morgan, he utilizes this as a convenient organism for genetic studies and soon in his lab, it became the fly room - another advantage as to why Morgan used fruit flies is because it only has 4 pairs of chromosomes which are easily distinguishable using a light microscope - There are 3 pairs of autosomes from the 4 and the other pair would be the sex chromosome - The female fruit fly would usually pair with the homologous x chromosome and males would have 1 x chromosome and 1 y chromosome - these early experiments provided convincing evidence that the chromosomes are the location of mendel's heritable factors - Morgan's discovery of a trait that correlated with the sex of flies was key to the development of the chromosome theory of inheritance - in humans and some other animals, there is a chromosomal basis of ses determination. There are 2 varieties of sex chromosomes: aa larger X chromosome ando - smaller Y chromosome - - A person with 2 X chromosomes develops as a female, while a male develops from a zygote with one X and one Y - Morgan's discovery of the trait among fruit flies started with the color of the eye which is white and then correlated it with the sex of flies and this provided important support for the chromosome theory of inheritance because the identity of the sex chromosome in an individual could be inferred by observing the sex of the fly, the behavior of the 2 members of the pair of sex chromosomes could be correlated with the behavior of the 2 alleles of the eye color gene - A gene that is located on either sex chromosome is called sex-linked gene - X chromosomes have genes for many characters unrelated to sex, whereas most Y- linked genes are related to sex determination - X-linked recessive disorders are much more common in males than females  Some disorders caused by recessive allele on the X chromosome is humans Duchenne muscular dystrophy This is a genetic disorder which is characterized by progressive muscle degeneration due to alteration of a protein that helps keep muscles intact -&Linked genes tend to be inherited together because they are located near each other on the same = chromosome -Genes located on the ame chromosome that tend to be inherited together are called linked genes - The genetic findings of Mendel and Morgan relate to the chromosomal basis of recombination - offspring with a phenotype matching one of - the parental phenotypes are called parental E types - offspring with nonparental phonotypes (new combinations of traits) are called recombinant types, or recombinant - a 50% frequency of recombination is ② observed for any 2 genes on different chromosomes - Our understanding about crossing over during meiosis among Homologous chromosomes is based on the discovery of Morgan among the genes that can be linked but the linkage was actually incomplete because some recombinant phenotypes, were actually observed - Morgan discovered that genes can be linked, but the linkage was incomplete - because some recombinant phenotypes were observed - that mechanism was the crossing over of homologous chromosomes - Alterations of chromosome number or structure cause some genetic disorders - large-scale chromosomal alterations in humans and other mammals often lead to spontaneous abortions (miscarriages) of cause a variety of developmental disorders  Human disorders due to chromosomal alterations - Aneuploidy results from the fertilization of gametes in which nondisjunction occurred. Offspring with this condition have an abnormal number of a particular chromosome - nondisjunction, there would be this failure of chromosome to separate during meiosis - Breakage of a chromosome can lead to 4 types of changes in chromosome structure; deletion, duplication, inversion and translocation DELETION newly born child ↓ here a part of the chromosome is out Deletion , off so it becomes shorter as compared to a normall One A deleted. segment is Chromosomal deletion syndromes typically involve larger deletions that are usually visible on karyotyping. Chromosomal Duplication Ocopied twice I would produce longer chromosome since a segment is duplicated 00 00 - Segment is inverted so coding is affected (there would be a swap of segments between 2 chromosomes so swap of characteristics (most common lead to extra chromos one or less a chromosome - down syndrome (Trisomy 21) is an aneuploid condition that results from 3 copies of chromosome 21. This is nondisjunction - person would exhibit short stature, sometimes have discorrectable heart defects and developmental delays - another aneuploid condition that involves sex chromosome is Klinefelter syndrome - Klinefelter syndrome is the result of an extra chromosome in a male, producing XXY individuals - additional x chromosome on the sex chromosome - usually observed on males -Testes small, produce little or no sperm - sign and symptoms vary. Some have taller on average height, less muscle mass and sometimes have enlarged breast tissue - affected individuals may also have learning disabilities - Monosomy X, called turner syndrome, produces X0 females, who are sterile it is the only known viable monosomy in humans because when provided with estrogen replacement therapy, girls with Turner syndrome would develop secondary sex characteristics and would have typical intelligence -lack of chromosome in sex chromosome, only X  - The syndrome cri du chat (cry if the cat) results from a specific deletion in chromosome 5 - A child born with this syndromes severely intellectually disabled and hers a catlike cry; individuals usually die in infancy or early childhood - in chromosome 5, cone would have shorter length - Certain cancers, including chronic myelogenous (CML), are caused by translocations of chromosomes - happens when a reciprocal transaction happens during mitosis of cells that are precursors of white blood cells - translocation, there would be a swap another chromosome  HISTORY OF DNA - In 1953 , James Watson and Francis Crick introduced an elegant double-helical model for the structure of DNA DNA inheritance is the most celebrated molecule of our time - , the substance of ,. Hereditary information is encoded in DNA and reproduced in all cells of the body DNA program - This directs the development of biochemical , anatomical , physiological , and to some extent) behavioral traits Evidence that DNA can transform bacteria - before discovery of structure of DNA, there was already evidence that DNA can transform bacteria - the discovery of the genetic role of DNA began with research by Frederick Griffith in 1928 - he mixed heat-killed remains of the pathogenic strain with living cells of the harmless strain, save became pathogenic (transformation) - He used living S cells which are the smooth strain and this is pathogenic cuz cells have outer capsule that would protect the micouarganism from an animals immune system - he has a rough strain which are non-pathogenic and don't have capsule - to test for trait of pathogenicity, ne injected it into the 2 strains - The mouse dies (pathogenic one) and the other mouse is healthy (nonpathogenic) - The heat killed S cells from the control, mouse healthy - The mixture of heat killed S cells and living cell,, mouse dies cuz S cells transformed r cells as r cells gained capsule Evidence that viral DNA can program cells - More evidence for DNA as the genetic material came from studies ox viruses that infect bacteria radioactivity Ot remaine outside cells & - In conclusion the phage phage prokin , DNA would enter the bacterial radioactivity found inside calls & cells but phage moteins so cells did neet containing radioactive phage DNA, released new phages With some radioactive proploms I phage RNA These viruses that infects bacteria are actually called as bacteriophages meaning they are bacteria eaters or phages. Viruses are much simpler than cells and a virus is a little more than DNA or sometimes RNA that is enclosed by protective coat which is often simply protein. A virus is an infectious microbe consisting of a segment of nucleic acid (either DNA or RNA) surrounded by a protein coat. To produce more virus, a virus must infect a cell and take over its metabolic machinery Now, in this experiment. This was actually conducted by Alfred Hershey and Martha Chase and they used radioactive sulfur and phosphorus to trace the fates of protein and DNA of the T2 bacteria or T2 phages that would infect bacterial cells. They wanted to see which of these molecules would enter the cell and could ' reprogram athem to make more phages. They concluded that DNA which are actually the genetic material that is found in the phages and is not actually the protein Additional evidence that DNA is the genetic material - Erwin Chargaff (biochemist) reported that DNA composition varies from one species to the next and the number of A and T bases are equal and number of G and C bases are equal. - Based on this, the DNA was known to be a polymer of these nucleotides which have these 3 components which includes the nitrogenous base which are the adenine, guanine, cytosine and thymine. DNA also has this sugar called deoxyribose and a phosphate group so the base can be this adenine, thymine, cytosine and guanine. From this experiment, chargaft analyzed the base composition of the DNA from a different number of organisms as you can see in the table. He reported that the base composition of DNA actually varies from different organisms as you can see in the table. This evidence of molecular diversity among organisms which most scientists presumed to be absent from DNA made DNA a more credible candidate more the genetic material - Based on the experiment of chargatf and the discovery of the structure of DNA, eve have here the structure of the DNA in which nucleotides are the building blocks of DNA - nucleotides include the phosphate group, sugar pentode (deoxyribose), and nitrogenous bases - The nitrogenous bases include the purine and pyrimidines. The purine and the adenine and guanine. The pyrimidines are cytosine and thymine while if its an RNA, it is actually uracil. Thymine replaced by uracil for RNA - uracil is pyrimidine - For the sugar, the only difference with the RNA is that it has ribose sugar -4 nitrogenous bases - DNA structure runs from 5' end to 3' direction in which we have here a nitrogenous base that is attached to a sugar and each sugar is actually attached with a phosphate backbone Structure of DNA - DNA molecule is made up of 2 strands, forming a double helix - complementary base paining A-T (U) and 2 hydrogen bonds that will form with it G-C and there would he 3 hydrogen bonds that would form - each nucleotide attaches to the 3-prime end via phosphate group - anti-parallel because it one strand runs from 5' to 3', the other strand will run from 3' to 5' - the reason why its a double strand is because we have the nitrogenous bases which are either purine or pyrimidine. They are actually complementary to each other and pair by means of this hydrogen bond. DNA replication - since the 2 strands of DNA are complementary, each strand acts as a template for building a new strand in replication - in DNA replication, the parent molecule unwinds (separate), and 2 new daughter strands are built based on base-pairing rules - DNA replication is a means on how DNA is actually increasing in terms of the number - The process of DNA replication actually occurs through a semicansenuctive model - semiconservative model of replication products that when a double helix replicates, each daughter molecule will have one old strand (derived or "conserved" from the parent molecule) and one newly made strand. Old strand will act as template for new strand. -In order for a new strand to form, the DNA strand should unwind first - Replication begins at particular sites called origins of replication, where the 2 DNA strands are separated, opening up a replication bubble. - At the end of each replication bobble is a replication fork, a Y-shaped region where new DNA strands are elongating - helicases are enzymes that untwist the double helix at the replication fork and is assisted by single-strand binding proteins in order for these two strands to be and remain separated - single-strand binding proteins bind to and stabilize single-stranded DNA. Maintain single strand