General Zoology PDF

GENERAL ZOOLOGY Enables scientists to determine the function Module 1: The Fundamental Units of each organelles. Eukaryotic and Prokaryotic Cells...

GENERAL ZOOLOGY Enables scientists to determine the function Module 1: The Fundamental Units of each organelles. Eukaryotic and Prokaryotic Cells of Life Basic features of all cells ○ Plasma membrane All organisms are made up of cells. ○ Semifluid substance (cytosol) The cell is the simplest collection of matter ○ Chromosomes that can be alive. Carry genes All cells are related by their descent from ○ Ribosomes earlier cells. Make proteins Cells can differ substantially from one Prokaryotic Cells another, yet they share common features. No nucleus Microscope DNA is found in the nucleoid Light microscope No membrane-bound organelles. ○ Visible light passes through a Cytoplasm is bound by a plasma membrane. specimen and then through the glass lenses. Lenses refract the light and the image is magnified. ○ Can magnify up to about 1,000 times the size of the actual specimen. Light Microscope Bright field Phase-contrast Differential-inferential-contrast. Fluorescence. Confocal Deconvolution Eukaryotic Cells Super-resolution. DNA is in a membranous nuclear envelope. Electron Microscope With membrane-bound organelles. Scanning Cytoplasm is located in the region between Transmission plasma membrane and nucleus. Used to study subcellular structures. 2 types ○ Scanning Electron Microscope (SEM) Focus the electron beams on the surface of the specimen. Provides 3D images. ○ Transmission Electron Microscope (TEM) Used to study internal structures of Cells. Cell Fractionation Takes cells apart and separates the major organelles from one another. Prokaryotic Cells No true nucleus.  GENERAL ZOOLOGY Lacks nuclear membrane Nuclear Envelope separates the contents of Genetic material is in a nucleic region the nucleus and the cytosol (nucleoid). Nuclear Membrane is a semipermeable Eukaryotic Cell membrane acting as a barrier that allows With true nucleus the passage of some molecules while Bounded by nuclear envelope blocking others from entering. Genetic material within the nucleus. Contains cytoplasm with cytosol and ○ Nucleolus membrane-bound organelles. Located within the nucleus May vary in numbers in a Cell Parts nucleus. The site of ribosomal RNA PLASMA MEMBRANE (rRNA) synthesis. Selective barriers that allow a sufficient passage of oxygen, nutrients, and waste to The pores regulate the entry and exit of service the volume of every cell. molecules from the nucleus. Nuclear size of the envelope is lined by the nuclear lamina. ○ Composed of proteins. NUCLEUS ○ Maintains shape of the nucleus. "Information Central" Contains most of the cell's genes. RIBOSOMES Usually the most conspicuous organelle. “Protein Factories” Complexes made of ribosomal RNA and ○ Nuclear envelope protein. Encloses the nucleus Carry out protein synthesis in 2 locations. Separates the nucleus from ○ Cytosol the cytoplasm Free ribosomes ○ Nuclear membrane ○ Outside the endoplasmic reticulum A double membrane or the nuclear envelope Each membrane consists of a Bound ribosomes lipid layer. Nuclear Envelope Vs. Nuclear Membrane  GENERAL ZOOLOGY Surface is studded with ribosomes. ENDOMEMBRANE SYSTEM SMOOTH ENDOPLASMIC RETICULUM Regulates protein traffic and performs Functions metabolic functions in the cell. ○ Synthesizes lipids Made up of ○ Metabolizes carbohydrates ○ Nuclear envelope ○ Detoxifies drugs and poisons. ○ Endoplasmic reticulum ○ Stores calcium ions. ○ Golgi apparatus ROUGH ENDOPLASMIC RETICULUM ○ Lysosomes Function ○ Vacuoles ○ Has bound ribosomes which secrete ○ Plasma membrane. glycoproteins (proteins covalently bound to carbohydrates). ○ Distributes transport vesicles Secretory proteins surrounded by membranes. ○ A membrane factory of the cell. GOLGI APPARATUS “The Shipping and the Receiving Center” Made up of flattened membranous sacs. ○ Cisternae Functions ○ Modifies products of the ER. ENDOPLASMIC RETICULUM ○ Manufactures certain “Biosynthetic Factory” macromolecules. Accounts for more than half of the total ○ Sorts and packages materials into membrane in many eukaryotic cells. transport vesicles. Continuous with the nuclear envelope. 2 distinct regions ○ Smooth ER Lacks ribosomes ○ Rough ER  GENERAL ZOOLOGY “Diverse Maintenance Compartments” Large vesicles derived from ER and Golgi apparatus Perform different functions in different cells. Types of Vacuoles ○ Food vacuoles Vacuoles that digest food particles ingested by the cell. ○ Contractile vacuole Found in many freshwater protists. Pump excess water out of the cells. ○ Central vacuole Found in many mature plant Cis Face cells. ○ “Receiving side of the golgi Hold organic compounds and apparatus.” water. Trans face ○ “Shipping side of the golgi MITOCHONDRIA AND CHLOROPLAST apparatus.” Both change energy from one form to another. LYSOSOMES Mitochondria “Digestive Compartments” ○ Sites of cellular respiration A membranous sac of hydrolytic enzymes Metabolic process that uses that can digest macromolecules. oxygen to generate ATP. Lysosomal enzymes work best in the acidic Chloroplast environment inside the lysosome. ○ Found in plants and algae. Hydrolytic enzymes and lysosomal ○ Sites of photosynthesis. membranes are made by the Rough ER. ○ Then transferred to the golgi apparatus for further process. ○ Mitochondria and chloroplast have some similarities with the bacteria. Enveloped by a double membrane Contain free ribosomes and circular DNA molecules. Grow and reproduce somewhat independently in cells. VACUOLES  GENERAL ZOOLOGY ENDOSYMBIONT THEORY CYTOSKELETONS Suggests that an early ancestor of Network of fibers that organizes structures eukaryotes engulfed an oxygen-using non and activities in the cell. photosynthetic prokaryotic cell. Help support the cell and maintain its shape The engulfed cell formed a relationship with 1. Microtubules the host cell, becoming an endosymbiont. ○ Thickest of the 3 components The endosymbiont evolved into ○ Hollow tubes mitochondria. ○ Functions: At least one of these cells may have then Maintains the cell shape taken up a photosynthetic prokaryote, Cell motility which evolved into a chloroplast. Chromosome movement in cell division Organelle movements. ○ Microtubules The centrosome has a pair of centrioles Each with 9 triplets of microtubules arranged in a ring. ○ Cilia and flagella Microtubules control the MITOCHONDRIA beating of flagella and cilia, “Chemical Energy Conversion” microtubule-containing They have a smooth outer membrane and extensions that project from an inner membrane folded into cristae. some cells. Inner membrane creates 2 compartments. Cilia and flagella differ in ○ Intermembrane space their beating patterns. ○ Mitochondrial matrix 2. Cilia and flagella Common structure PEROXISOMES ○ A core of microtubules Specialized metabolic compartments. sheathed by the plasma Produce hydrogen peroxide and convert to membrane. water. ○ A basal body that anchors Its relationship with other organelles is still the cilium or flagellum. unknown. ○ A motor protein called dynein, which drives the  GENERAL ZOOLOGY bending movements of cilium ○ Anchorage of nucleus and some or flagellum. other organelles. ○ Formation of nuclear lamina. How dynein “walking” moves cilia and flagella? Dynein arms alternately grab, move, and release the outer microtubules. Protein cross-link limit sliding. Forces exerted by dynein arms cause doublets to curve, bending the cilium or flagellum. 3. Microfilaments Actin filaments in our muscles Thinnest Functions ○ Maintenance of cell shape ○ Changes in cell shape ○ Muscle contraction ○ Cell motility ○ Division of animal cells Intermediate Filaments Fibers with diameters in a middle range. Fibrous proteins coiled into cables Functions: ○ Maintenance of cell shape  GENERAL ZOOLOGY Module 2: Extracellular Matrix of Animal Cells Animal cells lack cell walls but are covered by an elaborate extracellular matrix (ECM). The ECM is made up of glycoproteins such as collagen, proteoglycans, and fibronectin. ECM proteins bind to receptor proteins in the plasma membrane called integrins. Cell Membrane Plasma Membrane Cell Junctions Boundary that separates the living cell from Tight Junctions its surroundings. ○ Members of neighboring cells are Exhibits selective permeability pressed together, preventing (semi-permeable) leakage of extracellular fluid. ○ Allows some substances to cross the Desmosomes membrane more easily than other ○ “Anchoring junctions” substances. ○ Fasten cells together into strong sheets. Gap Junctions ○ “Communicating junctions” ○ Provide cytoplasmic channels between adjacent cells. Cell membranes are fluid mosaics of lipids and proteins. ○ Phospholipids Most abundant lipid in the plasma membrane. Amphipathic molecules Contain both hydrophilic and hydrophobic regions. A phospholipid bilayer can exist as a stable boundary  GENERAL ZOOLOGY between 2 aqueous Most lipids, and some proteins, drift compartments. laterally. Rarely would a lipid flip-flop transversely across the membrane. Membrane Proteins PIT Proteins determine most of the membrane’s Bilayer of phospholipid. specific functions. Hydrophilic head ○ Peripheral protein - Likes water. Bound to the surface of the Hydrophobic tail membrane. - Dislikes water. Not embedded within the phospholipid bilayer. Tails are kinked due to double bonds involved in ○ Integral protein structure. Penetrate the hydrophobic core. Fluid Mosaic Model (Plasma Membrane) Embedded in the A membrane that is a fluid structure with a phospholipid bilayer. “mosaic” of various proteins embedded in it. ○ Transmembrane protein ○ Proteins are not randomly Integral proteins that span distributed in the membrane. the membrane. 6 Major Functions of Membrane Proteins 1. Transport - Lipids move constantly but do not displace. Fluidity of the Membranes Phospholipids in the plasma membrane can move within the layer.  GENERAL ZOOLOGY 2. Enzymatic activity 5. Intercellular Joining 3. Signal Transduction a. Transduction is defined as the process of converting something, 6. Attachment to the cytoskeleton and especially energy or a message into extracellular matrix (ECM) another form. 4. Cell-cell recognition  GENERAL ZOOLOGY HIV resistance A typical HIV virus requires two receptors (CD4 receptor and CCR5 co-receptor) As long as both receptors are present along the plasma membrane of our cells, the HIV Our membranes have their distinct inside virus may attach to said receptors, thereby and outside faces. allowing the HIV virus entrance into the cell. Asymmetrical distribution of proteins, lipids, However, if only the CD4 is present along and associated carbohydrates within the the plasma membrane, while the CCR5 plasma membrane. co-receptor remains absent, the HIV virus Proteins are formed within the ER and will will only attach itself to the CD4 receptor, be carried by the cis face of the golgi thereby not being granted entrance into the apparatus toward the golgi apparatus. cell. Inside the apparatus, it will be segregated. The trans face will now be handling the Role of Carbohydrates in Cell-Cell Recognition distribution of the proteins using transport Cells recognize each other by binding to vesicles. molecules, often containing carbohydrates, on the extracellular surface of the plasma Permeability of the Lipid Bilayer membrane. Membrane carbohydrates may be Hydrophobic covalently bonded to lipids (glycolipids) or ○ Can dissolve in the lipid bilayer and more commonly to proteins (glycoproteins). pass through the membrane rapidly. Carbohydrates on the external side of the Hydrophilic. plasma membrane vary among species, ○ Includes ions and polar molecules individuals, and even cell types in an that do not pass the membrane individual. easily. Transport Proteins Allows the passage of hydrophilic substance across the membrane. Channel Proteins (tunnel) ○ With a hydrophilic channel, certain molecules can use a tunnel. Aquaporins Facilitate the passage of water.  GENERAL ZOOLOGY Passive Transport Substances diffuse down their concentration gradient. No work must be done to move the substances down the gradient (no energy used) Osmosis is an example of passive transport. Carrier Proteins (change) Osmosis ○ Bind to molecules Diffusion of water across the selectively that change shape to permeable membrane from the region of shuttle them across lower solute (salt for example) the membrane. concentration to the region of higher solute. concentration until the concentration is equal on both sides. High concentration of water (low solute) to low concentration of water (high solute) Diffusion Movement of molecules from an area of higher concentration to an area of lower concentration without any energy investment. Higher → lower, no energy investment (without use of ATP). The tendency for molecules to spread out evenly into the available space. Water Balance of Cells without Cell Walls Tonicity - Ability of a surrounding solution to cause a cell to gain or lose water. ○ Isotonic Solution Solute concentration is the same as inside the cell. No net movement of water across the membrane. ○ Hypertonic Solution (water out of the cell) Solute concentration is Molecules move toward the non-crowded areas to greater outside the cell. achieve balance on both sides.  GENERAL ZOOLOGY Since solute is greater outside (low water), water goes outside the cell. HIGH TO LOW Cells lose water. High concentration of water leaves the cell Cell shrivels up or shrinks. Lose water, shrinks ○ Hypotonic Solution (water into the cells) Solute concentration is less than the inside of a cell. Since solute is greater inside (low water), water goes inside the cell. HIGH TO LOW Cells gain water. Facilitated Diffusion Cells may swell or burst. Transport proteins speed up the passive Gain water, bursts movement of molecules across the plasma membrane. ○ Carrier Proteins (change) Undergo subtle change in shape that translocates the solute-binding site across the membrane. ○ Channel Proteins (tunnel) Provide corridors to allow specific molecules to cross the membranes. ○ Aquaporin Facilitate diffusion of water. ○ Ion Channel Facilitate diffusion of ions. Some are known as gated channels. Osmoregulation They open and close Control of solute concentrations and water in response to balance. stimulus. Needed for organisms that have problems with the hypertonic or hypotonic environments.  GENERAL ZOOLOGY Protein has to open itself for three sodium ions to attach themselves. ATP approaches the carrier protein and leaves phosphate. Once this happens, it closes in the cell and opens up outside the cell to release the three sodium ions. After which, two potassium ions will attach themselves in the carrier protein. Closes up on the outside and opens up on the inside to release two potassium ions. Three sodium ions out, two potassium ions in Active Transport LOW TO HIGH Moves substances against their concentration gradient. Requires energy, usually in the form of ATP. LOW TO HIGH, need energy Performed by specific proteins embedded in the plasma membrane. Allows cells to maintain concentration gradients that differ from their surroundings. Sodium-potassium pump is one type of the active transport. Passive transport Diffusion Facilitated Diffusion Active Transport Involve the use of ATP in the movement of molecules from a higher concentration area to a lower concentration area. Outside a cell, usually there should be a high amount of sodium ions and a low amount of potassium. Whereas, inside the cell there should be a lower amount of sodium ions and a higher amount of potassium ions. Carrier proteins have two parts ○ Half circle and v shape Membrane Potential ○ Carries molecules  GENERAL ZOOLOGY Voltage difference across a membrane. ○ Created by differences in the distribution of positive and negative ions across a membrane. Electrochemical Gradient 2 combined forces. Drive the diffusion of ions across a membrane. ○ Chemical force Ion’s concentration gradient. ○ Electrical force Uniport Effect of membrane potential Symport and antiport (cotransport) on the ion’s movement. Electrogenic Pump Bulk Transport A transport protein that generates voltage. Movement of proteins or macromolecules ○ Sodium-potassium pump into and out of the cell. Major electrogenic pump for Requires energy animal cells. 2 types ○ Proton pump ○ Exocytosis Major electrogenic pump for ○ Endocytosis plants, fungi, and bacteria. Exocytosis Help store energy that can be used for Transport vesicles migrate to the cellular work. membrane, fuse with it, and release their contents outside the cell. Many secretory cells use exocytosis to export their products. Out of the cell Endocytosis Cells take in macromolecules by forming vesicles from the plasma membrane. Cotransport Into the cell Coupled transport by a membrane protein 3 types Occurs when active transport of a solute ○ Phagocytosis indirectly drives transport of other Cell eating substances. ○ Pinocytosis Cell drinking ○ Receptor-mediated endocytosis Phagocytosis Cell engulfs a particle in a vacuole. The vacuole fuses with a lysosome to digest the particle. Pinocytosis  GENERAL ZOOLOGY Molecules dissolved in droplets are taken up Catabolic Pathway when extracellular fluid is “gulped” into tiny Release energy by breaking complex vesicles. molecules into simpler compounds. Receptor-Mediated Endocytosis Binding of ligands to receptors triggers vesicle formation. Redox Reactions: Reduction and Oxidation ○ Ligand Transfer of electrons during chemical Any molecule that binds reactions releases energy stored in organic specifically to another molecules. receptor site of another The released energy is ultimately used to molecule. synthesize ATP. Oxidation ○ Substance loses electrons. Reduction ○ Substance gains electrons. ○ Amount of positive charge is reduced. Reducing agent ○ Electron donor Oxidizing agent ○ Electron acceptor Some redox reactions do not transfer electrons but change the electron sharing in covalent bonds. Cellular Respiration Metabolism The totality of an organism’s chemical reactions. The cells extract energy and apply it to perform work. Metabolic pathway ○ Starts with a specific molecule ○ Ends with a product. During cellular respiration, fuel is oxidized and oxygen is reduced. GENERAL ZOOLOGY  GENERAL ZOOLOGY Glycolysis Breaks down glucose into 2 molecules of Module 3: Cellular Respiration pyruvate Occurs in the cytoplasm Includes both aerobic and anaerobic 2 major phases respiration. ○ Energy investment phase ○ But often used to refer to aerobic ○ Energy payoff phase respiration. Can occur with or without the presence of ○ Anaerobic does not involve oxygen. oxygen (Anaerobic) Carbohydrates, fats, and proteins are consumed as fuel. ○ Help to trace cellular respiration with glucose. C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy (ATP + Heat) Adenosine triphosphate (ATP) ○ Key player in cellular respiration ○ Energy source for all cells ○ Considered as the “energy currency” of the cell. ○ Releases large amounts of energy when converted to adenosine diphosphate (ADP). Nicotinamide adenine dinucleotide (NAD+)/nicotinamide adenine dinucleotide + hydrogen (NADH). Flavin adenine nucleotide (FAD/FADH2) 3 Stages of Cellular Respiration Glycolysis ○ Breaks down glucose into 2 molecules of pyruvate. Citric Acid Cycle ○ Completes the breakdown of glucose. Oxidative Phosphorylation ○ ATP synthesis. Krebs Cycle Citric Acid Cycle/Tricarboxylic Acid Cycle In the presence of oxygen, pyruvate enters mitochondria. ○ Oxidation of glucose is completed  GENERAL ZOOLOGY Pyruvate is converted to acetyl Coenzyme A NADH and FADH2 produced by the cycle (acetyl CoA) relay electrons extracted from food to the The cycle oxidizes organic fuel derived from ETC. a single pyruvate. ○ 1 ATP ○ 3 NADH ○ 1 FADH2 Oxidative Phosphorylation ETFC occurs at the cristae of the mitochondrion. Most of the chain’s components are proteins Carriers alternate in reduced and oxidized states as they accept and donate electrons. Electrons drop in free energy as they go down the chain and are finally passed to oxygen, forming water. TCA has 8 steps ○ Each catalyzed by a specific enzyme.  GENERAL ZOOLOGY Chemiosmosis Use of energy in a H+ gradient to drive cellular work. Electrons transfer in the ETC causes proteins to pump H+ from the mitochondrial matrix to the intermembrane space. H+ moves back across the membrane, passing through the synthase. ATP synthase uses the exergonic flow of H+ to drive phosphorylation of ATP. Accounting of ATP Production During cellular respiration, ost energy flow in this particular sequence; ○ Glucose → NADH → ETC → Proton-motive Force →ATP  GENERAL ZOOLOGY Most cellular respiration requires oxygen to Fermentation produce ATP 2 common types Without the presence of O2, the electron ○ Alcoholic fermentation transport chain (ETC) will not push through. ○ Lactic acid fermentation ○ Glycolysis will couple with anaerobic respiration or fermentation to Alcoholic Fermentation produce ATP. Pyruvate is converted to ethanol in 2 steps ○ Release of carbon dioxide. Anaerobic Respiration ○ Production of ethanol Uses ETC with a final electron acceptor Uses yeast other than oxygen Brewing, winemaking, baking. Uses sulfate rather than oxygen to produce ATP. Fermentation ○ Uses substrate-level phosphorylation instead of ETC to produce ATP. Anaerobic Respiration Obligate anaerobes ○ Carry out fermentation ○ Cannot survive in the presence of oxygen. Facultative anaerobes ○ Yeast and many bacteria. Lactic Acid Fermentation ○ Can survive using either Pyruvate is reduced to NADH. fermentation or cellular respiration. End product: lactate ○ Pyruvate is a fork in the metabolic No carbon dioxide is released. road that leads to two alternative Process where fungi or bacteria are used to catabolic routes. make cheese and yogurt. Human muscle cells use lactic acid fermentation to generate ATP when oxygen is scarce.  GENERAL ZOOLOGY Versatility of Catabolism Catabolic pathways funnel electrons from many kinds of organic molecules into cellular respiration. Glycolysis accepts a wide range of carbohydrates. Proteins must be digested to amino acids. ○ Amino groups can feed glycolysis or the Krebs cycle. Fats Glycerol ○ Glycolysis Fatty acid ○ Used in generating acetyl CoA in lieu of pyruvate. ○ Broken down by beta oxidation.  GENERAL ZOOLOGY Oogonia ○ Egg cell / ovum (ova) Module 4: Cell Cycle MITOSIS The ability of the organisms to produce more of its own kind best distinguishes the Cell Cycle Consists of: living things from nonliving things. Mitotic phase Cell division ○ 10% of the cycle ○ Continuity of life based on the Interphase reproduction of cells. ○ 90% of the cycle Unicellular Organisms Interphase Division of one cell reproduces the whole 3 subphases organism. ○ G1 Multicellular Organisms First gap Depend on cell division for ○ S Phase ○ Development “Synthesis” ○ Growth Repair ○ G2 “Second gap” G1 Increase cell growth. Increase in number of cytoplasmic structure ○ Mitochondria number and cytoskeletal structure. Doubling in the number of centrosomes. Preparation for mitosis. Chromatid and Chromatid = sister chromatids Some cells carry the destined cell. Mitosis S Phase Division of genetic material in the nucleus. DNA synthesis Cytokinesis G2 ○ Division of the cytoplasm. Biochemical preparation for the onset of Meiosis mitosis. Produces gametes. G0 Yields non-identical daughter cells that have Normal stage half as many chromosomes as the parent Will not go to mitosis. cell. Nerve cells, heart muscle cells. Spermatogonia ○ Sperm cells  GENERAL ZOOLOGY Mitotic Spindle Chromatin condenses into chromosomes. Structure made of microtubules that Centrosomes move toward the opposite controls the chromosome movement during poles of the cell. mitosis. Prometaphase Spindle microtubules Beginning of the metaphase stage. Its assembly begins with the centrosome. Late prophase, early metaphase. ○ Centrosome replicates during Chromosomes start to align themselves at interphase. the equatorial region or metaphase plate. ○ Forms 2 centrosomes that migrate to opposite ends of the cell during prophase and prometaphase. Aster ○ Radial array of short microtubules. ○ Extend from each centrosome. ○ Spindle = centrosome + spindle microtubules + aster Kinetochores ○ Protein complexes associated with centromeres. METAPHASE All chromosomes are aligned at the middle (equatorial region or metaphase plate). Spindle fibers hold chromosomes in place. Spindle fibers originate from the centrosomes located at the opposite poles. Along your chromosomes, spindle fibers are attached to the kinetochore proteins. ANAPHASE Sister chromatids are separated and pulled apart by the spindle fibers toward the opposite poles, producing daughter chromosomes. TELOPHASE and Cytokinesis Appearance of cleavage furrow. Chromatids will start expanding to form chromatin fibers. G2 Formation of nuclear envelope. Preparing the cell for mitosis DNA material here is referred to as Cytokinesis chromatin fibers. Cleavage furrow will move toward the middle of the cell to complete cell division. PROPHASE Nuclear envelope starts to disintegrate. After this, they will undergo interphase again.  GENERAL ZOOLOGY Prokaryotes Binary Fission ○ Cell division of prokaryotes ○ Cell simply replicates DNA and divides. ○ Once DNA replicates, two origins appear at each end of the cell. ○ Replication finishes. ○ Two daughter cells results. Spermatogonia Sperm cells Oogonia Egg cells Asexual vs Sexual Reproduction Asexual Reproduction Single individual passess all of its genes to its offspring without fusion of gametes. Sexual Reproduction 2 parents give rise to offspring that have unique combinations of genes inherited from the parents. MEIOSIS Chromosomes in Human Cells Cell division of sex cells. Human somatic cells have 23 pairs of Living organisms are distinguished by their chromosomes. ability to reproduce their own kind. Karyotype ○ An ordered display of the pairs of Heredity chromosomes form a cell. ○ Transmission of traits from one ○ Individual’s complete set of generation to the next. chromosomes Variation ○ Homologs (homologous ○ Exhibited by the differences in chromosomes) appearance that offspring show 2 chromosomes in a pair. from parents and siblings. These chromosomes are of the same length and shape. Carry genes controlling the same inherited characters.  GENERAL ZOOLOGY Develops into an adult. Only the x and y chromosomes differ. Sex Chromosomes / Allosomes Determines the gender of the individual. X or Y Human females: XX Human males: XY Autosomes The remaining 22 pairs of chromosomes. At sexual maturity, the ovaries and testes produce Diploid Cell haploid gametes 2 sets of chromosomes Gametes are only produced through ○ 2n meiosis. ○ Humans: 2n = 46 Meiosis results in one set of chromosomes in each gametes. Haploid Cell Gametes contain a single set of Meiosis chromosomes. Reduces the number of chromosomal sets ○ n from diploid to haploid. ○ human s: n = 24 Preceded by the replication of chromosomes. Takes place in 2 consecutive cell divisions ○ Meiosis I ○ Meiosis II ○ Both result in 4 daughter cells, instead of 2 daughter cells like in mitosis. Each daughter cell has only half as many chromosomes as the parent cell. Fertilization Union of gametes or sex cells (sperm cell and egg cell). Zygote Fertilized egg Has one set of chromosomes from each parent. Produces somatic cells by mitosis.  GENERAL ZOOLOGY First Meiosis Division of homologous chromosomes Second Meiosis Division of sister chromatids Metaphase I Pair of homologs line up at the metaphase plate/equatorial region and each chromosome faces opposite poles. Microtubules from 1 pole are attached to the kinetochore of 1 chromosome of each tetrad. Meiosis I 4 phases ○ Prophase I ○ Metaphase I ○ Anaphase I ○ Telophase I and Cytokinesis Prophase I Each chromosome pairs with its homolog and crossing over occurs–synapsis, Site of crossing-over is referred to as the chiasmata. Chiasmata Anaphase I ○ X-shaped regions Pair of homologous chromosomes separate. ○ Site of crossover  GENERAL ZOOLOGY One chromosome of each pair moves towards the opposite poles, guided by the spindle apparatus. Sister chromatids remain attached at the centromere and move as one unit toward the pole. Meiosis II Telophase I and Cytokinesis 4 phases Each half of the cell has a haploid set of Prophase II chromosomes. Metaphase II ○ Each chromosome is still made up of Anaphase II two sister chromatids. Telophase II and Cytokinesis Cytokinesis occurs simultaneously Prophase II ○ Forms 2 haploid daughter cells. Formation of spindle apparatus. In late prophase II, chromosomes move toward the metaphase plate. Metaphase II Sister chromatids are arranged in the metaphase plate. Due to the crossing over in meiosis I, the sister chromatids are no longer genetically identical. Kinetochores of the sister chromatids attach to microtubules extending from opposite poles. Anaphase II Sister chromatids separate.  GENERAL ZOOLOGY ○ Move toward the opposite poles as 2 Metaphase I newly individual chromosomes. Chromosomes line up as homologous pairs on the metaphase plate. Anaphase I Homologs separate from each other; sister chromatids remain joined at the centromere. Telophase II Chromosomes arrive at the opposite poles. Formation of nuclei. Chromosomes begin decondensing. Genetic Variation Behavior of chromosomes during meiosis and fertilization is responsible for most of the variation that arises in each generation. 3 mechanisms contribute to genetic variation. Independent assortment of chromosomes. Crossing over Random fertilization Independent Assortment of Chromosomes Homologous chromosomes orient randomly at Metaphase I. In an independent assortment, each pair of 3 Events Unique to Meiosis chromosomes sorts maternal and paternal Prophase I homologs into daughter cells independently Each homologous pair undergoes synapsis of the other pairs. and crossing-over between nonsister Independent assortment is the process chromatids with the subsequent where the chromosomes move randomly to appearance of chiasmata. separate poles during meiosis. A gamete  GENERAL ZOOLOGY will end up with 23 chromosomes after The fusion of two gametes produces a meiosis, but independent assortment means zygote with any of about 70 trillion diploid that each gamete will have 1 of many combinations. different combinations of chromosomes Cell Cycle Control System Directs the sequential events of the cell cycle. Regulated both by internal and external controls. Has specific checkpoints ○ Cycle stops until a go-ahead signal is received. These checkpoints allow the cell to continue progressing their particular cycle. Crossing Over Crossing over produces recombinant chromosomes, which combine DNA inherited from each parent. Crossing over contributes to genetic variation by combining DNA from two parents into a single chromosome. In humans, an average of one to three crossover events occurs per chromosome. 2 Regulatory proteins Cyclin Cyclin-dependent kinase (Cdk) Activity of Cdk rises and falls with changes in concentration of its cyclin partner. Maturation-promoting factor (MPF) Cyclin-Cdk complex that triggers a cell’s passage past the G2 checkpoint into the M phase. For many cells, the G1 checkpoint is the most Random Fertilization important. Random fertilization adds to genetic If cells receive a go signal at G1 checkpoint variation because any sperm can fuse with It will complete the S1, G2 and M phases and any ovum (unfertilized egg). divide.  GENERAL ZOOLOGY Cancer cells that are not eliminated by the If cells do not receive a go signal immune system. Cells with exit cycle Masses of abnormal cells within normal Switch into a nondividing state. tissue. ○ G0 Benign Tumor ○ Abnormal cells remain only at the original site. ○ Have an enclosure which keeps it in place in its particular location. Malignant Tumor ○ Invade surrounding tissues and can metastasize (spread). Export cancer cells to other parts of the body. Benign tumors have blood vessels which siphon blood and nutrients. External factors that influence cell division Growth factors ○ Released by certain cells. ○ Stimulate other cells to divide. Density-dependent inhibition ○ Crowded cells will stop dividing. Cancer Cells Do not respond to the body’s control mechanisms. Do not need growth factors to grow and divide. ○ They make their own growth factor. ○ They may convey a growth factor’s signal without the presence of the growth factor. ○ They may have an abnormal cell cycle control system. Transformation Process where normal cell is converted into cancerous cell. Tumors  GENERAL ZOOLOGY Module 5: Introduction to Genetics Deoxyribonucleic Acid Genetic material Polymer of nucleotides Each consists of: ○ Nitrogenous base ○ Sugar ○ Phosphate group Erwin Chargaff Reported that DNA composition varies from Therefore: one species to another. The Watson-Crick model explains the Chargaff’s rule Chargaff’s rule: in any organism, the ○ In any species, the number of A and amount A = T, and G = C. T bases are equal and the number of G and C bases are also equal. ○ Adenine (A) = Thymine (T) ○ Guanine (G) = Cytosine James Watson and Francis Crick Introduced the double-helical model structure based on Rosalind Franklin’s X-ray crystallography of the DNA molecule. Determined that adenine (A) is paired only with thymine (T), and guanine (G) is paired only with cytosine (C).  GENERAL ZOOLOGY Base Pairing 2 strands of DNA are complementary ○ Each strand acts as a template for DNA in eukaryotes are linear shaped. building a new strand in replication. Multiple origins of replication. ○ Parent molecule unwind → 2 new All will open up and start replicating to form daughter strands. two daughter DNA molecules. Watson and Crick’s semiconservative model Replication fork of replication predicts that when a double Y-shaped regional the end of each helix replicates, each daughter molecule will replication bubble where new DNA strands have one old strand and one newly made are elongating. strand. Helicases DNA Replication Enzymes that untwist (straighten) the Replication begins at particular sites called double helix at the replication fork. origins of replication, where the two DNA Single-Strand binding proteins strands are separated, opening up a Bind to and stabilize single-stranded DNA. replication “bubble”. Topoisomerase Replication proceeds in both directions from Corrects “overwinding” ahead of replication each origin, until the entire molecule is forks by breaking, swiveling, and rejoining copied. DNA strands. Primase Enzyme for the initiation of the RNA chain. Adds RNA nucleotides one at a time. DNA Polymerase Catalyze the elongation of the new DNA at the replication fork.  GENERAL ZOOLOGY Antiparallel Elongation The antiparallel structure of the double helix affects the replication. DNA polymerases only add nucleotides to the free 3’ end of a growing strand. ○ Newly formed strands can only elongate in the 5’ and 3’ direction. Replicating the Ends of DNA Molecules Limitations of DNA polymerase create problems for the linear DNA of eukaryotic chromosomes. The usual replication machinery provides no way to complete the 5’ ends, so repeated Parts of the DNA strand rounds of replication produce shorter DNA Leading strand molecules with uneven bonds. Lagging strand Okazaki fragment Leading Strand DNA strand synthesized by the DNA polymerase that moves toward the replication fork. Lagging Strand DNA polymerase working on a new DNA strand away from the replication fork. Okazaki Fragment Segments formed from the lagging strand. Later on joined by the DNA ligase.  GENERAL ZOOLOGY Telomeres Principles that Account for Passing of Traits from Special nucleotide sequences found at the Parents to Offspring eukaryotic chromosomal DNA ends. “Blended” Hypothesis Do not prevent shortening of DNA ○ Genetic material from 2 parents molecules. blend together. Postpone the erosion of genes near the DNA “Particulate” Hypothesis molecules. ○ Parents pass discrete heritable units It has been proposed that the shortening of (genes). telomeres is connected to aging. Character Heritable features that vary among individuals. Flower color Trait Each variant for a character. Purple or white color of flower.  GENERAL ZOOLOGY Mendel reasoned that only purple flower factor was affecting flower color in the F1 hybrids. ○ Purple flower color = dominant trait. ○ White flower color = recessive trait. The factor for white flowers was not diluted or destroyed because it reappeared in the F2 generation. True-Breeding Plants that produce offspring of the same variety when they self-pollinate. “P-generation” (parental generation). Hybridization Mating of 2 contrasting, true-breeding varieties. F1 Generation Mendel observed the same pattern of “First Filial Generation” inheritance in six other pea plant Hybrid offspring of the P (parental) characters, each represented by two traits. generation. What Mendel called a “heritable factor” is F2 Generation what we now call a gene. “Second Filial Generation” When F1 individuals self pollinate or cross-pollinate with other F1 hybrids. Law of Segregation States that only one of the two gene copies present in an organism is distributed to each gametes (egg or sperm cell) that it makes, and the allocation of the gene copies is random. When Mendel crossed contrasting true-breeding white-and purple- flowered pea plants, all of the F1 hybrids were purple. When Mendel crossed the F1 hybrids, many of the F2 plants had purple flowers, but some had white. Ratio of about three to one, purple to white flowers, in the F2 generation.  GENERAL ZOOLOGY Homozygous Organisms with 2 identical alleles for a Allele character. Alternative versions of a gene that accounts Heterozygous for variations in inherited characters. Organisms with 2 different alleles for the Dominant Allele gene controlling the character. ○ Determines the organism’s Not true-breeding. appearance. Recessive Allele ○ No noticeable effect on appearance. Punnett Square Can show the possible combinations of the sperm and egg. Dominant allele is represented by an uppercase letter. Recessive allele is represented by a lowercase letter. Phenotype ○ Physical appearance. Genotype ○ Genetic makeup  GENERAL ZOOLOGY Example: States that each pair of alleles segregates ○ PP and Pp plants have the same independently of each other pair of alleles phenotype (purple) but different during gamete formation. genotypes. Applied only to genes on different, Testcross nonhomologous chromosomes or those far Used to determine the genotype. apart on the same chromosome. Genes located near each other on the same chromosome tend to be inherited together. Inheritance Patterns are often more complex predicted by simple Mendelian Genetics The relationship between genotype and phenotype is rarely as simple as in the pea plant characters. Many heritable characters are not determined by only one gene with two alleles. However, the basic principles of segregation and independent assortment apply even to more complex patterns of inheritance. Law of Dominance Complete Dominance Monohybrid Cross ○ Occurs when phenotypes of the A cross between such heterozygotes. heterozygote and dominant Dihybrid Cross homozygote are identical. A cross between F1 dihybrids. ○ Examples include having a specific Can determine whether two characters are hair color, skin pigment, and brown transmitted to offspring as a package or eyes. independently. Incomplete Dominance ○ Phenotype of F1 hybrids is somewhere between the phenotypes of the two parental varieties. ○ Blending or mixing of the two phenotypes ○ Example: if a white and black dog produce a gray offspring. Codominance ○ 2 dominant alleles affect the phenotype in separate, distinguishable ways. ○ Example: Roan cow; it has both the white hairs and the reddish-brown hairs. Law of Independent Assortment Developed from using the dihybrid cross.  GENERAL ZOOLOGY Most genes exist in populations in more than two allelic forms. ○ The four phenotypes of the ABO blood group in humans are determined by three alleles. Pleiotropy Most genes have multiple phenotypic effects, a property called pleiotropy. ○ Ex: Sickle-Cell Disease In homozygous individuals, all hemoglobin is abnormal. The Relation Between Dominance and Phenotype Heterozygotes are usually A dominant allele does not subdue a healthy but may suffer some recessive allele; alleles don’t interact that symptoms. 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 are not necessarily more common in populations than recessive alleles. Ex: one baby out of 400 in the United States Epistasis is born with extra fingers or toes. A gene at one locus alters the phenotypic The allele for this unusual trait is dominant expression of a gene at the second locus. to the allele for the more common trait of Ex: coat color of animals. five digits per appendage. ○ Depends on 2 genes In this example, the recessive allele is far 1 gene for pigment color. more prevalent than the population’s 1 gene determines if pigment dominant allele. will be deposited in the hair. Multiple Alleles  GENERAL ZOOLOGY Pedigree ○ 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. Polygenic Inheritance An additive effect of two or more genes on a single phenotype. Skin color in humans is an example of polygenic inheritance. Recessive Inherited Disorders Many genetic disorders are inherited in a recessive manner. ○ Range from relatively mild to life-threatening. ○ Show up only individuals homozygous for the allele. Albinism ○ Recessive condition characterized by a lack of pigmentation in skin and hair. 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 environment history. Many human traits follow Mendelian patterns of inheritance. Pedigree Analysis  GENERAL ZOOLOGY Dominantly Inherited Disorders The Central Dogma Some human disorders are caused by Theory stating that genetic information dominant alleles. flows only in one direction, from DNA, to Cause lethal diseases but are rare RNA, to protein, or RNA directly to protein. ○ Arise by mutation Explains the flow of genetic information Achondroplasia from DNA to RNA to make a functional ○ A form of dwarfism caused by a rare product. dominant allele. ○ Protein. 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. Fetal Testing Amniocentesis ○ Liquid that bathes the fetus (amnion) is removed and tested. ○ Amnion is aspirated and checked for genetic problems through biochemical testing. ○ Also used for karyotyping. Chorionic Villus Sampling (CVS) ○ A sample of the placenta is removed and tested.  GENERAL ZOOLOGY Module 6: Animal Form and Contains cells that are closely jointed together. Functions Function: Camouflage ○ Protein Strength ○ Absorption Speed ○ Secretion Toxins Shape may be Animals are multicellular, heterotrophic ○ Squamous eukaryotes with tissues that develop Usually regulates the different embryonic layers. passage of molecules in and Heterotrophs out of cells through diffusion. ○ Absorb organic molecules or ingest ○ Cuboidal large food particles. Absorption and secretion of Characteristics substances (ex: kidney). Animals are multicellular eukaryotes Hormones Cells lack cell walls ○ Columnar Bodies are held together by structural Help absorb nutrients that proteins such as collagen. pass through the stomach Nervous & muscle tissues are unique and small intestine. ○ Defining characteristic of animals Tissues Group of similar cells that act as a functional unit. Tissues Arrangement Epithelial Tissues ○ Simple Covers the outside of the body. Lines the organs and cavities within the body.  GENERAL ZOOLOGY Main function is to bind and support other tissues Most are vascularized. Contains sparsely packed cells scattered throughout the extracellular matrix ○ ECM is composed of fibers in a liquid, jelly-like or solid foundation. ○ Stratified ○ Different proteins and salts can be found here. Different cells: ○ fibroblasts which secrete different proteins ○ Macrophages which are involved in the immune system. ○ Pseudostratified 3 Types ○ Collagenous Fibers Provide strength and flexibility ○ Reticular Join connective tissue with its adjacent. ○ Elastic Fibers Stretch and snap back to the original length. Connective Tissue Major types of connective tissue  GENERAL ZOOLOGY ○ Loose connective tissue ○ Fibrous connective tissue ○ Adipose Tissue ○ Blood ○ Bone ○ Cartilage Areolar/Loose Connective Tissue Binds epithelia to underlying tissues Holds organs in place Fibrous Connective Tissue Tendons ○ Attach muscles to bones Blood Ligaments Red blood cells, erythrocytes ○ Connective bones of the joints ○ Humans’ RBCs do not contain nucleus White blood cells, leukocytes ○ For immunity Platelets, thrombocytes from megakaryocytes ○ cell fragment Fluid connective tissue Adipose Bones Fat cells called adipocytes Mineralized connective tissue Stores fat for insulation and fuel. Make up the skeleton Nucleus is displaced by the fat to the side of the cell, giving the cell a ring-like appearance. Cartilage Strong and flexible support material  GENERAL ZOOLOGY Nervous Tissue Functions in the receipt, processing, and transmission of information. Neurons (nerve cells) ○ Transmit nerve impulses Glial cells (glia) ○ Support cells Muscle Tissue Responsible for nearly all types of body movement Made up of actin and myosin ○ Enables the muscles to contract. 3 types ○ Skeletal muscle Striated, unbranched, multinucleated, voluntary ○ Smooth muscle No striations, unbranched, 1 nucleus, involuntary ○ Cardiac muscle Striated, branched, intercalated discs, 1-2 nuclei, involuntary. Intercalated discs support the synchronized contractions of cardiac cells.  GENERAL ZOOLOGY Module 7: Integumentary System Dry, dead layer that helps prevent the infiltration of infectious microorganisms as Functions well as prevents dehydration. Protects the underlying organs and tissues Provides protection from abrasions for the Maintains body temperature. more delicate epidermis layers. Synthesizes Vitamin D3. Stratum Lucidum Stores lipids Found only in places with thick skin on our Detects touch, pressure, pain, and body. Palms, soles, heels, digits, or fingers. temperature. Stratum Granulosum Excretes salt, water, and organic wastes. Grainy appearance under the microscope. Protects the body against infection. Grainy due to its capability of generating Mammalian skin and its modification large amounts of keratin. distinguish the mammals as a group. Stratum Spinosum Mammals’ body is mostly covered with hair Spiny in appearance or fur. Spines are due to the protruding cell ○ Some with reduced coverage. processes that join cells. ○ Presence of sweat, scent, and Spines allow it to communicate with sebaceous glands. adjacent cells through desmosomes. ○ Underneath the skin is a thick layer Stratum Basale or Germinativum of fat.