Biology 189 Final Exam Study Guide PDF

Biology 189 Comprehensive Final Exam Study Guide Ch. 1 - Classification - Domains of Life - Bacteria & Archaea - Prokaryote - No nucleus - No membrane-bound organelles - Eukarya - Has a nucleus...

Biology 189 Comprehensive Final Exam Study Guide Ch. 1 - Classification - Domains of Life - Bacteria & Archaea - Prokaryote - No nucleus - No membrane-bound organelles - Eukarya - Has a nucleus - Membrane-bound organelles - Mitochondria and lysosomes - 4 Kingdoms - Protista - Has a nucleus - Uni/multi-cellular - No specialized tissue - Ex: - Algae - Fungi - Absorbs nutrition - Uni: yeast - Multi: mushroom - Cell wall - Plantae - Photosynthetic - Multicellular - Cell wall - cellulose - Animalia - Non-photosynthetic - Multicellular - NO cell wall - Most consume food - Prokaryotic cells - No nucleus - Has a cell wall - Pili & Flagella - Plasmid & Capsule - Eukaryotic cells - Has a nucleus - Mitochondria - Rough/Smooth - Cell Membrane - Diversity, properties of life and unity of life - Have order -\> organization - Process energy - Adapt to changes in environment - Respond to the environment - Grow and develop - Reproduce - Regulation - Levels of Biological Organization - Molecules - A group of atoms bonded together - Ex: - H2O, O2, NaCl - Organelles - One or more specific jobs to perform in a cell - Ex: - Mitochondria, nucleus, lysosomes - Cells - Smallest structural & functional unit of an organism - Ex: - Nerve, muscle, bacteria, and plant cells - Tissue - Group of similar cells, working together to perform - Ex: - Connective, epithelial, muscle - Organs - Collection of tissues that form a functional unit to perform - Ex: - Heart, lungs, liver, etc. - Organism - Any living thing - Ex: - Humans, plants, animals, & fungi - Population - Group of same species gathered - Ex: - A herd of zebras, colony of seals - Communities - Group of different species interacting - Ex: - Forest of trees & plants - Ecosystem - Living organisms interacting w/non-living - Ex: - Amazonian jungle - Biosphere - Encompasses all living organisms and environment - Ex: - Rainforest, coral reef, mountain range - Themes of Biology - Organization - Structure and function are correlated at ALL levels of biological organization - Cells - Organisms basic units of structure & function - [Emergent properties]: - Arrangement & interaction of parts - Information - DNA - The heritable info to continue life - Lens cells to crystallin proteins - DNA -\> mRNA -\> chain of amino acids -\> proteins - Energy of matter - Flow of energy - Energy comes from the sun - Passes from: - Plants (producers) - Plant eater (consumers) - Animal eaters (consumers) - Interactions - Organisms interact w/their environments, exchanging matter & energy - Human interaction w/bacteria, normally does not cause disease - [Feedback mechanisms] - Regulate biological systems - Negative - Decrease reaction - Positive - Increases reaction - Evolution (Core Theme) - Species change over time - Traits better adapted to their environment - Increase survival - Increase the number of offspring - More organisms w/that train w/in the species Ch. 2 - Subatomic particles - Proton - Determines element - Electron - 1/2,000 Dalton - Neutron - 1 Dalton = 1 Neutron - Types of chemical bonds - Covalent bond - The sharing of a pair of valence electrons by 2 atoms - Everyone wants a full outer shell - Electronegativity - Attraction of a given atom for the electrons of a covalent bond - Polar - Atoms have different electronegativity - One atom "hogs" the electron - Creates "partial" charge - Non-polar - Atoms share near equal electronegativity - Share electrons equally - NO partial charges - Ionic bond - Forms when an atom strips electrons from their bonding partners - Attraction by opposite electrical charge - Ions are charged - Noncovalent bonds - Hydrogen bonds - Forms when hydrogen bonds to an electronegative atom - NO sharing of electrons - Van der Waal interaction - Asymmetrically distributed electrons in nonpolar covalent bonds - Weak but many Ch. 3 - The structure of water - Hydrogen bonding - H2O molecule is a polar molecule - Opposite ends have opposite charges - Emergent properties of water - Cohesive behavior - Attraction - Hydrogen bonds - Cohesion - H2O -\> H2O - Adhesion - H2O -\> anything else - [Surface tension] - Is a measure of how hard it is to break the surface of a liquid - Molecules at the surface from stronger bonds - Ability to moderate temperature - High specific heat - Amount of heat to absorb a change of temperature - Lots of hydrogen bonds = more chemical energy needed to break the bonds - Cools environment - Keeps stable temperature - The environment - Your body - Aquatic organisms - High heat of vaporization - Heat absorbance to change from liquid -\> gas state - Lots of heat to break hydrogen bonds - Evaporate cooling - Sweat evaporates = cooling down - Expansion upon freezing - Lower temperature = less movement - Stable hydrogen bonds - Molecules further apart - Ice less dense - Insulates water below ice and allows life to exist below the ice - Versality as a solvent - Solution - Homogeneous misture of substances - Solvent - Dissolving agent - Solute - Substance that is dissolved - Aqueous solution - Water in the solvent - 2 ways to dissolve a solvent w/water: - Formation of hydration shell - Making hydrogen bonds - Hydration shell - Keeps ions apart - Protein solubilization - By formation of hydration shell and hydrogen bonds - Water is a solvent for biological fluids - Blood - Sap - Liquids in cells - pH, acids and bases - pH - potential of hydrogen - used to describe whether a solution is acidic or basic - range: - 0 - Most acidic - 14 - Most basic - 7 - neutral - acids - contribute H+ to a solution - ex: hydrochloric acid - acid in stomach - aids in digestion - ex: acetic acid - vinegar - has higher concentration of H+ than OH- - bases - accept H+ - some chemicals accept hydrogen ions (H+) & remove them from a solution - ex: sodium hydroxide (NaOH) - provides OH- that combines w/H+ to produce H2O - this reduces the H+ concentration - Buffers - Are molecules that have small changed in pH - Can have lethal consequences - Ex: blood pH - Are substances that minimize changes in concentrations of H+ & OH- in a solution Ch. 4 - formation of bonds with carbon - organic molecules contain carbon - each carbon is bonded to 4 other atoms - 2 carbon atoms can form a double bond - Ex: - Methane - (CH4) - Ethane - (C2H6) - Ethylene - (C2H4) - Carbon chains form the skeleton of most organic molecules - Chains may vary in length and shape - Carbon rings can fuse with each other - Properties of hydrocarbons - (hydrophobic or nonpolar) - Organic molecules consisting of only carbon & hydrogen - Can release a large amount of energy - structure and name 7 common functional groups - hydroxyl (-OH) - polar due to electronegativity in oxygen - ex: - ethanol - carbonyl (C = O) - sugars with a ketone group are called [ketones] - aldehydes are called [aldoses] - ex: - acetone/ketone - propanal/aldehyde - carboxyl (\--COOH) - acts as an acid - ex: - acetic acid - carboxylate ion - amino (-NH2) - acts as a base - ex: - glycine - ionized form of NH2 - sulfhydryl (-SH) - 2 (-SH) groups can react, forming a "cross-link" that helps stabilize protein structure - Ex: - cysteine - Phosphate (-OPO2\^2-) - Contributes negative charge - When attached, confers on a molecule the ability to react w/ H2O, releasing energy - Ex: - Glycerol phosphate - methyl (-CH3) - affects the expression of genes - affects the shape & function of sex hormones - ex: - methyltyrosine Ch. 5 - dehydration reaction to build polymers and hydrolysis to break them down to monomers (building blocks) - dehydration reaction - to build - when a water molecule is lost during the connecting monomers - hydrolysis - to break down - reverse [dehydration reaction] - water breakage: - **polymers -\> monomers** - **H+** attaching to one monomer & **OH-** attaching to another - Ex: - Digestion - **Dehydration reactions** & **Hydrolysis** - Can be involved in the formation & breakdown of other molecules that are not **polymers**, like **lipids** - Recognize structures and know functions of the 4 major biological macromolecules - Carbohydrates - [Definition]: - Includes sugars & polymers of sugars - Monosaccharides - Molecular formula: - CH2O - Has a [carbonyl] group & multiple [hydroxyl] group - Size of carbon skeleton: - 3 to 7 carbons long - 6 carbons - hexoses - 5 carbons - pentose - 3 carbons - Triose - Cellular respiration - Cells extract energy from glucose molecules by breaking them down in a series of reactions - Disaccharides - 2 [monosaccharides] joined by **glycosidic linkage** - Covalent bond formed between 2 monosaccharides by a **dehydration reaction** - Ex: - Maltose - Sucrose - Lactose - Must be broken down into monosaccharides to be used for energy by organisms - Polysaccharides - Definition: - Polymers with 100 or 1,000 [monosaccharides] joined by **glycosidic linkages** - Serve as storage material, hydrolyzed as needed to provide monosaccharides for cells - Serve as building material for structures that protect the cell or the whole organism - Storage polysaccharides - Plants store **starch** as granules w/in cellular structures known as plastids - A polymer of glucose monomers - Joined by 1-4 linkages - Amylose or amylopectin - **Glycogen** (animals) - a polymer of glucose; more extensively branched - vertebrates store **glycogen** mainly in liver and muscle cells - Structural polysaccharides - **Cellulose** (dietary fiber) - A major component of the tough walls that encose plant cells - It is the most abundant organic compound on earth - In **starch** - All glucose monomers are in the A configuration - In **cellulose** - All glucose monomers are in the B configuration (upside down) - **Chitin** - Carb used by insects to build their exoskeleton - Similar to cellulose, w/B linkages, except that the glucose monomer of chitin has a [nitrogenous] -- containing attachment - Lipids - Definition: - Do not form polymers because they are **hydrophobic** - Do not mix well with water - Based on their molecular structure - Consist mostly of [hydrocarbons region] with relatively nonpolar C -- H bonds - Include: - Waxes, fats, phospholipids & steroids - fats (triglycerides) - definition: - consists of a **glycerol** molecule joined to 3 fatty acids - is an **alcohol**; each of its 3 carbons bears a **hydroxyl group** - fatty acids - has a long carbon skeleton; 16-18 carbons - one end: **carboxyl group**; the rest: **hydrocarbon** - fats separate from water because of the water molecules **hydrogen-bond** to one another & exclude the fats - ex: - olive oil w/ aqueous vinegar solution - **ester linkage** - fatty acid molecule is joined to glycerol by a dehydration reaction - bond between **hydroxyl & carboxyl group** - saturated fats - definition - no double -- bonds between carbon atoms composing a chain - as many hydrogen atoms as possible are bonded to the carbon skeleton - unsaturated fats - definition - 1 or more double bonds, w/1 fewer hydrogen atoms on each double -- bonded carbon - **Cis-double bonds** - major function: - **energy storage** - a gram of **fat** stores more than twice as much energy as a gram of a **polysaccharide** - phospholipids - definition: - essential for cells because they are major constituents of cell membranes - similar to a fat molecule but has only [2 fatty acids] attached to **glycerol** rather than 3 - 2 ends of phospholipids show different behaviors - [Hydrocarbon tails] - Inside "bilayer" - [Phosphate group & attachments] - Hydrophilic head - Outside "bilayer" - Steroids - Definition: - Are lipids characterized by a carbon skeleton consisting of 4 fused rings - **Cholesterol** - Crucial molecule in animals - Different steroids are distinguished by the particular [chemical groups] attached to this ensemble of rings - Proteins - Definition - Is a biologically functional molecule made up of one more polypeptide, each folded & coiled into a specific 3-dimensional structure - General formula - **[RCH(NH2)COOH]** - many functions: - speed up chemical reactions - defense - storage - movement - transport - cellular communication - structural support - Life would not be possible w/o enzymes, most of which are proteins - Catalysts - Chemical agents that selectively speed up chemical reaction's w/o being consumed in the reaction - Has a unique 3-dimensional shape - Has the same set of [20 amino acids,] linked in unbranched polymers - The bond between **amino acids** is called a **peptide bond**, so a polymer of amino acids is called a **polypeptide** - Amino acids - Definition: - An organic molecule w/both an [amino group] and a [carboxyl group] - R-group (side chain) - Determines the unique characteristics of a particular amino acid, affecting its functional role of a polypeptide - **Nonpolar side chains** - Are hydrophobic - **Polar side chains** - Is hydrophilic - [Basic amino acids] - Amino groups in their side chains that are generally positive in charge - [Acidic amino acids] - Side chains that are generally negative in charge due to the **carboxyl group** - Peptide bond formation - 2 amino acids positioned - **Carboxyl \ amino** - **Dehydration reaction** - Resulting bond - **Covalent** is called a **peptide bond** - Polypeptide backbone - Repeating sequence of atoms - Range in length: - 1,000 or more amino acids - Free amino group - **N-terminus** - Free carboxyl group - **C-terminus** - Cells can make many different polymers by linking a limited set of monomers into diverse sequences - 4 levels of [protein structure] - Definition - A protein's specific structure determines how it works - Primary - Sequence of amino acids - Determined by inherited genetic information - Dictates [secondary] structure & [tertiary] structure - Due to the chemical nature of a backbone and the side chains of the amino acids along the polypeptide - Secondary - Definition - Repeatedly coiled or folded in patterns that contribute to the proteins overall shape - Result of hydrogen bonds between the components of the **polypeptide backbone** - **O-** have partial [negative charge] - **H+ - N** partial [positive charge ] - A helix - Delicate coil held together by **hydrogen bonding** in 4^th^ amino acid - B pleated sheet - 2 or more segments of the **polypeptide chains** - Tertiary - Definition - The overall shape of a polypeptide resulting from interactions between the side chains (**R groups**) of the various [amino acids] - Hydrophobic interactions - Caused by the exclusion of nonpolar substances by water molecules - Explanation - As a **polypeptide** folds into its functional shape, **amino acids** w/[hydrophobic] (nonpolar) side chains usually end up in clusters at the core of the **protein**, out of contact w/water - Nonpolar amino acids - Side chains are close together - **Van der Waals interactions** - Help hold them together - Polar side chains - **Hydrogen bonds** - Positive & Negative Charge - **Ionic bonds** - Disulfide bridges - Definition - Form when 2 **cysteine monomers**, which have [sulfhydryl groups (-SH)] on their side chains are brough close together by folding of the **protein** - May further reinforce the shape of a **protein** - Quaternary - Definition - The overall protein structure that results from the aggregation of these polypeptide chains - Ex: collagen - Fibrous protein that has 3 identical helical polypeptides intertwined into a larger triple helix giving the long fibers great strength - Connective tissue in skin, bone, tendons, ligaments, and other body parts - nucleic acids - definition - are polymers made of monomers called **nucleotides** - **gene** - unit of inheritance - 2 types of [nucleic acids] - **DNA** - Provides directions for its own replication - Directs [RNA synthesis] - [Messenger RNA] - Conveys genetic instructions for building proteins from the [nucleus] to the [cytoplasm] - Different forms: - Naked DNA - No proteins (histone) associated - Chromatin - Uncondensed DNA w/histones (proteins) - Chromosome - Condensed DNA - Chromatid - Replicated chromosomes (copied) - Ex: - Sister chromatids - Sugar: - Deoxyribose - Lacks an oxygen - **RNA** - Controls protein synthesis - **Gene expression** - Sugar: - Ribose - **Nucleotides** - Polynucleotide consists of monomers - Composed of 3 parts: - Pentose - Nitrogenous base - 1 to 3 phosphate groups - [Polynucleotide] - Nucleic acids are macromolecules that exist as polymers - [Nucleoside] - Portion of a nucleotide w/o any phosphate groups - [Nitrogenous bases] - 1 or 2 rings that include nitrogen atoms - 2 families: - **Pyrimidine** - 1 six-membered ring of carbon and nitrogen atoms - Ex: - Cytosine, thymine & uracil - **Purines** - 6-membered ring fused a 5-membered ring - Ex: - Adenine & guanine - [Functions] - DNA Replication - Direct protein synthesis Ch. 6 - functions of the following components and organelles (animal vs plant) - lysosome - digestive organelle where macromolecules are hydrolyzed - **cristae** - in folding of the inner membrane - proteins of electron transport chain - endoplasmic reticulum - rough and smooth - rough = [ribosome-studded] - network of membranous sacs & tubes - active in membrane synthesis and other metabolic processes - mitochondria - organelle where [cellular respiration] occurs & most ATP is generated - chloroplast (plants) - converts energy to chemical energy stored in sugar molecules - Golgi apparatus - Organelle active in synthesis, modification, sorting, and secretion of cell products - Cytoskeleton - Reinforces cell's shape - Has: - Microfilaments - Intermediate filaments - Microtubules - Plasma membrane - Selectively permeable - Ribosome - Complexes that make proteins - Free in cytosol or bound to **rough ER** or **nuclear envelope** - Small brown dots - Nucleus - **Nuclear envelope** - Double membrane (w/ER) - **Nucleolus** - Non-membranous structure involved in production of ribosomes - **Chromatin** - Consists of **DNA** & **proteins** Ch. 7 - major structural components of cell membrane -- phospholipids and proteins - Biological membrane - in an aqueous environment, phospholipids form a [bilayer] - hydrophobic "tails" pack together - hydrophilic "head" face outward, where they interact w/water - Phospholipids - amphipathic - hydrophobic & hydrophilic - Van der Waal interaction - movement - move 2 different ways - lateral - flip-flop - common strategy for drugs to enter cell - Fluidity of Membranes - Affected temperature - **Homeostasis** - Cell membrane maintains consistent fluidity - Composition of saturated and unsaturated [fatty acids] - Cholesterol - Temperature buffer - **Warm temp.** - Restrains movement - **Cool temp.** - Maintains fluidity by preventing tight packing - Fluid - Unsaturated hydrocarbon tails w/kinks - Viscous - Saturated hydrocarbon tails - Packed tightly - Single bond - Fluid mosaic model - mosaic pattern of proteins embedded in membrane - transport proteins involved - 2 ways water move in & out of the cell - **Osmosis** - Movement of water by [diffusion] - **Facilitated diffusion** - Movement through an aquaporin - Includes: - Phospholipids - Cholesterol - Proteins - Carbohydrates - integral and peripheral proteins - **Integral** - penetrate the hydrophobic core - span the membrane - [transmembrane proteins] - hydrophobic region - 1 or more stretches of nonpolar amino acids, alpha helices - **Peripheral** - Bound to membrane surface - permeability of lipid bilayer - selectively permeable - osmosis - movement of water by **diffusion** - water balance: - tonicity - the ability of a solution to cause a cell to gain or lose water - hypotonic - solute concentration is **less** than inside the cell - cell gains water - isotonic - solute concentration is the **same** as inside the cell - hypertonic - solute concentration is **greater** than that inside the cell - cell loses water - passive and active transport - **Passive** - solute move **down** its concentration gradient - does not require energy - small molecules/transports proteins - **by diffusion** - molecules randomly are moving around, because they have **kinetic energy** - net movement from high tot low - **osmosis** - **facilitated diffusion** - movement of molecules aided by [transport proteins] - **Active** - solutes move **against** its concentration gradient - requires energy Ch. 8 - first and second laws of thermodynamics - **1^st^ law** - Energy of the universe is constant - Can be transferred/transformed - Cannot be created/destroyed - Principle of conservation energy - **2^nd^ law** - Every energy transfer or transformation increases the entropy of the universe - The more randomly arranged a collection of matter is, the greater the **entropy** - enzyme functions - effects of local conditions (temp & pH) - reaction rate increases w/increasing temperature - optimal temperature where rate is greatest - optimal pH: 6-8 - for most enzymes, there are exceptions - induce fit theory - a substrate binds to an active site, and both change shape slightly, creating an ideal fit for catalysis - competitive vs noncompetitive inhibitors - **competitive** - resemble the normal substrate and compete for admission into the active site - reduce the productivity of enzymes by blocking substrates - **noncompetitive** - binds to the enzyme away from active site - alters enzyme shape, affects active site function Ch. 9 - review the stages of cellular respiration - glycolysis - occurs in cytosol - has 2 major phases - energy investment phase - energy payoff phase - produces: (using 1 glucose molecule) - 2 pyruvates - 2 NADH - 2 ATP - pyruvate oxidation - completes the breakdown of glucose - citric acid cycle - occurs in [mitochondrial matrix] - produces: (using 1 pyruvate) - 4 NADH - 1 FADH2 - 1 ATP - 3 CO2 - oxidative phosphorylation (electron transport chain & chemiosmosis) - occurs in [mitochondrial matrix] - accounts for most of the ATP synthesis - produces: - 1 NADH -\> 1 NAD + ½ H2O / 2.5-3 ATP - 1 FADH2 -\> 1 FAD + ½ H2O / 1.5-2 ATP - Electron transport chain - The function is to break the large free -- energy drop from food O2 into smaller steps that release energy in manageable amounts - Electron transfer in the electron transport chain causes proteins to pump H+ from the mitochondrial matrix to the intermembrane space - Chemiosmosis - - substrate level phosphorylation vs oxidative phosphorylation - fermentation - uses **glycolysis** to generate 2 ATP - include reactions that regenerate NAD+ - 2 common types: - Alcohol fermentation - Produces alcohol in the form of ethanol - Occurs in yeast for making beer, wine, and bread - Lactic acid fermentation - Produces lactic acid - Occurs in human muscle cells during strenuous exercise - Uses phosphorylation instead of an electron transport chain to generate ATP Ch. 12 - The stages of mitosis (eukaryotic cell cycle) - Definition of mitosis - division of the nuclear material - DNA is divided - Interphase - Focused on building material to grow - G1 & G2 - Supplying/growing and synthesizing enough material to move on to the next phase - S for synthesis - DNA content is doubled by **DNA Replication** - Uncondensed chromatin - Prophase - first and longest phase - during which chromosomes become visible - centrioles appear and move to opposite poles - the nuclear membrane and nucleolus disappear - Prometaphase - the process that separates duplicated genetic material into two identical daughter cells - Metaphase - during which the chromosomes line up along the center of the cell - Anaphase - during which the chromatid arms separate and move to opposite ends of the cell - Telophase - during which TWO nuclei are visible - the chromosomes spread out as chromatin - the nuclear membrane and nucleolus return - mitotic spindle and centrioles disappear - Cytokinesis - Division of the cytoplasm - the cytoplasm is divided between the 2 new daughter cells - (animal cells, cleavage furrow, plant cells, cell plate) - Chromatin - Binary fission in prokaryotic cells only - produce genetically identical cells - The cell cycle and control system - **Cell cycle** - Defined as the period in which a cell has become a cell until it divides again - Analogous to the lifespan of a human - **Control System** - complex regulatory mechanism that ensures each phase of the cycle occurs correctly - often involving checkpoints to monitor critical processes like DNA replication - preventing uncontrolled cell division by pausing the cycle if errors are detected Ch. 13 - human autosomes (\#1-22) and sex chromosomes (X & Y) - **human autosomes** - 22 pairs of numbered chromosomes - **sex chromosomes** - chromosomes that determine an individual's sex by the genes it carries - females - XX - Males - XY - diploid (somatic cells) vs haploid cells (gametes) - **diploid (2n)** - somatic cells - has 2 sets of chromosomes - \# in 46 (2n = 46) - **haploid (n)** - gametes - contains a single set of chromosomes - \# is 23 (n=23) - homologous chromosomes, chromatids, and chromatin - **homologous chromosomes** - pairs of chromosomes that are inherited from parents - have the same genes in the same order, but may have slight variation - **chromatids** - identical copies of a chromosome that are formed when a chromosome\'s DNA is replicated in preparation for cell division - **chromatin** - during interphase, the DNA is found in this form - stages of meiosis - Prophase I - where the chromatin condenses into chromosomes - forms homologous pairs, **crossing over** occurs. - Exchange of genetic material - Metaphase I - where homologous chromosomes line up in the middle of the cell - attached to spindle fibers - independent assortment - Anaphase I - where homologous chromosomes are pulled apart by spindle fibers - move to opposite poles of the cell - Telophase I & Cytokinesis - Nuclear membranes form around the separated chromosomes - the cell divides into two haploid daughter cells - Prophase II - Mitotic division of the haploid cells - Chromosomes condense further - Metaphase II - sister chromatids line up at the equator of the cell - Anaphase II - Sister chromatids separate at the centromere - Move to opposite poles - Telophase II & Cytokinesis II - Nuclear membranes form around the separated chromatids - resulting in: - four haploid daughter cells - synapsis and crossing over - **synapsis** - the process where two homologous chromosomes pair up closely together during the prophase I stage of meiosis - allowing for the alignment of genes and facilitating genetic recombination (crossing over) between them - **crossing over** - the process where homologous chromosomes exchange genetic material during prophase I - resulting in: - the creation of new chromosome combinations - contributing significantly to genetic diversity among offspring in sexual reproduction Ch. 14 & 15 - dominant vs recessive - refer to the relationship between two versions of a gene, or alleles, that an individual inherits from their parents - A dominant allele masks the effect of the recessive allele - **Dominant** - allele that is expressed when two alleles of a gene are different - ex: - allele for brown eyes (B) is dominant - **Recessive** - allele that is not expressed when two alleles of a gene are different - recessive allele is typically only expressed when there is no dominant allele present - ex: - both alleles are for blue eyes (bb) - the individual will have blue eyes - homozygous vs heterozygous - **homozygous** - having two identical versions of a gene - **heterozygous** - having two different versions of a gene - solve problems for genetic crosses - complete dominance - means one allele completely masks the expression of another - ex: - the allele for purple flowers is completely dominant over the allele for white flowers - incomplete dominance - a blended phenotype where both alleles are fully expressed - ex: - When a red flower and a white flower are crossed, the offspring have pink flowers. - codominance - when both alleles are fully expressed simultaneously in the phenotype - neither allele is dominant over the other - ex: - the ABO blood group - where individuals with type AB blood express both A and B antigens on their red blood cells. - Autosomal dominant/recessive - **Dominant** - A trait is expressed when an individual has one copy of the mutant allele. - **Recessive** - A trait is expressed when an individual has two copies of the mutant allele. - X-linked dominant/recessive - **Dominant** - A trait is expressed when an individual has one copy of the mutant allele - **Recessive** - A trait is not usually expressed when there is a normal copy of the gene. Ch. 16 - Basic principle of DNA replication - DNA replication - Definition - Starts at a specific site on the DNA molecule called the **origin of replication** - A sequence of DNA on a DNA molecule that enzymes recognize & binds to an know this is the start of origin - semi-conservative - where each new strand is paired with an original strand - complementary base pairing - 5'ATTGATC3' - 3'TAACTAG5' - Are **antiparallel** - Run in opposite directions - 5' to 3' direction - DNA replication occurs in this order 1^st^ - Enzymes involve in DNA replication - Primase - Synthesizes RNA Primers - Sequence of RNA nucleotides - DNA ligase - an enzyme that joins DNA strands together by forming a phosphodiester bond - DNA polymerase III - Adds nucleotides in the 5' to 3' direction - Proofreads: - Initial error - 1 in 100,000 nucleotides - Error in completed DNA - 1 in 1 billion nucleotides - 2 repair mechanisms if proofreading fails: - **Mismatch repair** - Of DNA, repair enzymes (over 100) correct errors in base pairing - **Nucleotide excision repair** - A **nuclease** cuts out and replaces damaged stretches of DNA - DNA polymerase I - Removes RNA primer and replaces it w/DNA - helps connect [Okazaki fragments] by replacing ribonucleotides with DNA - Topoisomerase - Reduces the strain on the DNA strand - manages DNA topology by temporarily cutting and rejoining DNA strands - Helicase - Separates the 2 strands by breaking the **hydrogen bonds** - unwinding double-stranded DNA molecules into single strands by breaking the hydrogen bonds between base pairs - Single binding strand proteins - Protect the 2 strands from cleavage - Stabilize and prevents the strands from joining together - Leading vs lagging strand - Leading strand -\> replication fork - Lagging strand \