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BIO152H5 (69)


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University of Toronto Mississauga
Fiona Rawle

- Ahypothesis must be testable and falsifiable - Atheory is a well tested explanation for a more general phenomenon; hypothesis treat more specific observations - Heritable variation is the variation in characteristics caused by genetic factors. E.g. of heritable variation would be a disease (like skin cancer, etc) or eye colour. - The first meiotic division results in halving the amt of DNAin the cell - FOUNDER’S EFFECT: The establishment of a new population by a few original founders (in an  extreme case, by a single fertilized female) which carry only a small fraction of the total genetic  variation of the parental population - In mitosis, the number of chromosomes in the cell remain the same before and after mitosis - Speciation: genetic isolation, genetic drift and/or natural selection, divergence to two species - PROTEINS CAN BE BROKEN DOWN BY HYDROLYSIS - Speciation is the evolutionary process by which new biological species arise - Postzygotic isolation - Atype of reproductive isolation that occurs after members of two different species have mated and produced a hybrid offspring. Such hybrids are usually unable to reproduce. E.g. Mule - DNAis replicated in S-phase - Cell cycle: INTERPHASE [ G1 (first gap), S-phase (synthesis), G2 (second gap)], DIVISION (mitosis/meiosis) - G1: first sub phase of interphase. For many cells, this phase is the major period of cell growth during its lifespan. During this stage new organelles are being synthesized. - S-phase: S-phase (synthesis phase) is the part of the cell cycle in which DNA is replicated, occurring between G phase a1d G phase. 2 - G2: final sub phase of interphase. G pha2e is a period of rapid cell growth and protein synthesis during which the cell readies itself for mitosis. - Crossing over mostly occurs at the end of the chromosomes (meiosis) - Metaphase of mitosis: line up in a line - Metaphase I of meiosis: line up in pairs - ALLOPOLYPLOID: Having two or more complete sets of chromosomes derived from different species. - Selection acts on phenotypic (what you can see) variation; however, evolution depends on genotypic (gene) variation in the population. - Changes to the genotype of even one nucleotide can affect the phenotype. - SICKLE CELLANEMIA: changes in a single amino acid causes the red blood cells to change and become sickled - founder effect is the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population - Natural selection is not by chance or due to random events - Genetic drift by founder’s effect and bottle necks (environmental factors that decrease population) decrease variation - Somatic mutations occur in non-reproductive cells and won't be passed onto offspring - STABILIZING SELECTION is a type of natural selection in which genetic diversity decreases as the population stabilizes on a particular trait value. - directional selection is a mode of natural selection in which a single phenotype is favored, causing the allele frequency to continuously shift in one direction. - Disruptive selection : extremes are favoured - Natural selection influences evolutionary changes by... removing versions of genes based on their effects on reproductive success. LECTURE NOTES LEC 1: - Characteristics of living things/ Properties of Life: 1. Order and cellular organization, 2. Metabolism/Nrg Utilization, 3. Homeostasis and regulation 4. Growth development and reproduction 5. Heredity (crucial to sustain life) 6. Response to env (all living things respond to their env) 7. All living org evolve - CELL: highly structured compartment, surrounded by a plasma membrane, organelles, fluid where chem. Reactions take place (able to sustain itself) - CELL THEORY:All org are made of cells and all cells come from pre-existing cells. (Life has a beginning at the cell) - 2 hypothesis: Cells produce spontaneously OR only when pre-existing cells grow and divide - Pasteur disproved the spontaneous cell production hyp by experiments - EVOLUTION occurs when heritable variation leads to DIFFERENTIAL REPRODUCTIVE SUCCESS - THEORY OF EVOLUTION BY NATURAL SELECTION: why do species change? Striving to survive (adaptation), survive and have more offspring to which they can pass on their genetic advantages - NATURAL SELECTION explains how species that are related to one another change over time - 1858: Darwin & Wallace : all species are related and come from a common ancestor - HYPOTHESIS: educated guess; must be testable and falsifiable - Scientific Method: Observations, hypothesis, prediction, experimentation/testing, Conclusion - Experiments: contrived situations - Variables: factors that can change in value under different conditions - Independent variable: can be manipulated by the scientist - Dependent variable: not changed by the researcher - Control: what’s the point/- make sure that everything in your experiment is done to that control - Scientific Method: • Observations and measurements that others can repeat • Ideas/hypothesis that are testable by experiments that others can verify as well - Science is limited to things we can observe and test. Science: natural phenomenon - Sexual competition hypothesis true for giraffes: giraffes evolved long necks b/c males with longer necks win more fights than shorter neck giraffes and therefore have a higher chance of passing it on to their offspring - DARWIN’S theory of evolution was based on the following hypothesis: 1. Earth is very old; org have been changing throughout the history of life 2. All org are descendants of a single common ancestor 3. Species multiply by splitting into daughter cells 4. Evolution proceeds via gradual changes in populations 5. The major agent of evolutionary change is NATURAL SELECTION - Theory in science= certainty, in public= guess LECTURE 2: - Lamarck - first to use the term evolution - Wallace: younger than Darwin and came up with the same idea as D completely separate from D. D quickly published his work - Lamarck: “Inheritance ofAcquired characteristics” (characteristics are acquired over your lifetime) His e.q. of the giraffe was wrong - You can only pass on something that is genetic - not acquired - Variation in what is passed on - D first believed that all species were fixed (religious perspective) - Darwin: If you have more offspring than the env can support, then the individuals with slightly better characteristics can survive better. (competition among offspring- those who survive pass on their offspring - Darwin’s book 1859 “The origin of species by means of natural selection of the preservation of favoured races in the struggle for life” - Religious beliefs: life is only about 6000 years old (church), organisms are “irreducibly complex” or fixed- unchanging - Concept of intelligent design: has been used as an argument against Darwin. Cannot be explained by evolution; org are so complex that it’s hard to believe that they evolved from something simple(everything was purposefully made) - THEORY OF EVOLUTION IS ASCIENTIFIC THEORY B/C: • Of it’s broad applicability • Has been continuously validated by observations and experiments - Science and religion do not conflict because they address different types of questions LECTURE 3: - Macromolecules include: carbohydrates, proteins and nucleic acids, lipids - Evolution= unity and diversity of organisms - What do we have in common as organisms? Macromolecules - Carbohydrates: molecules of carbon, oxygen and hydrogen. Include: sugar, starch and fiber - Sources: fruits & veges, wheat, plants (rice) - Simple Carbs: Monosaccharide (Glucose- C H 0 ) and disaccharides (sucrose = fructose 6 12 6 + glucose) - Complex: Polysaccharides (consist of long chains of sugars) include: 1. Starch: form of nrg storage in plants 2. Glycogen: nrg storage in animals 3. Cellulose: found in cell walls of plants (has a function of more structural support) - Fiber: derived from plant material - Cellulose: most abundant compound on earth; we basically use it as roughage (to get rid of our waste); Can’t breakdown cellulose - Org that can breakdown cellulose have stomachs that are modified to break it down - Function of cellulose in plants: vigility and support - Function of chitin in insect exoskeleton: protections - GLYCOPROTEINS (carbs joined to proteins): Identification badge for cells- are key molecules of cell-cell recognition. Important in signalling & communicating with other cells - CARB FUNCTIONS: • building blocks in the synthesis of other molecules; • nutrients (source if nrg); • provide cells with fibrous structural materials; • indicate cell identity - Proteins: made up of amino acids - Amino acids: have a central carbon atom that bonds to: H N (a2ino group), COOH (carboxyl); H; R (side group) - Removal of water- dehydration; addition of water- hydrolysis - Primary structure of proteins: whatever order the amino acids are found in; unique LINEAE sequence of amino acids - Secondary structure: results from H bonding b/w carboxyl O2 of one a.a and the H of another a.a.Alpha helix or B-pleated sheets - Tertiary Structure: beding and folsing of the polypeptide chain; many bods are imp - Quaternary structure : complex shape; 2 or more polypeptide chain - Protein structure: provide shape and strength - Role of enzymes: speed up chemical reactions - Everything depends on the correct shape of the protein; form determines function - PRIONS: infectious proteins that are improperly folded; forms of normal proteains that don’t differ in a.a seq but in shape • Affects other proteins to be dysfunctional • Causes holes in the brain • Disease-causing: mad-cow, scrapie, chronic wasting disease, kure • Incurable • Form reflects function - Plant proteins are considered incomplete because they generally lack one or more of ESSENTIALAMINO ACIDS - EssentialA.A: cannot make ourselves; must obtain from food - All are available in milk, eggs meat but not ins veges - There are EIGHT essesntial a.a for humans - Nucleic acids: polymers of nucleotides that are composed of a phosphate group, a sugar group and a nitrogenous base - Sugars (DNAand RNA); bases: purines and pyrimidines - DNA- molecule of heredity ; made up of nucleotides - Four bases: thymine, cytosine, guanine, adenine (Awith T and G with C) - Gene Expression: use of info in DNAto direct the production of proteins (occurs in 2 stages) Transcription Translation DNA mRNA Protein - Transcription: One strand of the DNAis replicated by the RNApolymerase; 20 different a.s; Mrna CARRIES CODONS (3 letter codes) - Translation: converts the order of nucleotides in a gene into the order of a.a in a protein • Ribosomes translate mRNA • mRNAcarries the nucleotide code for the protein to be made • tRNAmolecules “interpret” the nucleotide code • Each tRNAcarries an a.a and an anticodon - GENETIC CODE: rules that govern translation - Mutations: Sequence of DNAbeing altered • Point Mutations:Alteration of one or a few bases (Base substitutions, insertion or deletion) • Frame-shift Mutations: Insertion or deletion that throw off the reading frame • Mis-sense Mutation: results in a totally different protein (substitution) • Nonsense (truncation) get a non-functional protein • Silent Mutations: end up getting the same a.a; protein is the same - Anticodon goes the opp way as the mRNA, so the same way as DNA(since mRNA sequences is opposite of the DNA) - Start codon: MET – methionine - STOP codons: UAA, UGAAND UAG - MUTATION: (ultimate) source of variation upon which natural selection can work on - EVOLUTION: Change in genetic structure of org over time (works on that variation) LECTURE 4 - LIPIDS: 3 types; steroids; phospholipids; fats - L have a small hydrophilic comp and a large hydrophobic component - Steroids: • Distinguished by a 4 ring structure • Essential molecule in cell membranes • Production of hormones - Fats: • Nrg storage; eg. triglyceride • Imp nutrient: nrg supply for cells; • Optima way of long-term nrg storage (hibernation) - Phospholipids: • Polar head and a long hydrophobic non-polar tail • Foundmostly in our plasma membrane • 2 fatty acid chains - Unsaturated Fat: not saturated with enough H. C=C, bent shape; liq at room temp. Less than the max # of H atoms - Saturated fats; max # of H atoms, C-C. Linear shape allows easy stacking. Solid at room temp - Fats AND phospholipids differ in: fatty acids chain lengths and degree of saturation/unsaturation - MEMBRANE PERMEABILITY is affected by: 1. Hydrocarbon chain length 2. # of double bonds - If you are an animal in the arctic you want the max UNSATURATION (thus, their plasma membrane com differs) - Lipid bilayers are selectively permeable ( small molecules like O2, CO2 and even H2O can pass in & out and transport proteins help bigger molecules - Lipid bilayers with MANY unsaturated fatty acids have HIGHER permeability - Integral proteins: extend from the top to the bottom (interact with the entire membrane) - Peripheral Proteins sit at the top and bottom - Membrane lipids as well as some proteins areAMPHIPATHIC (hydrophobic in some parts and hydrophilic at other parts) - Amphipathic proteins can integrate into lipid bilayers - Membrane carbs: glycolipids & glycoprotein – located on the outer surface of membrane recognition sites - Glycolipids attatch to the lipid component of the bilayer - LIPIDS: physical integrity of the membrane; create majority of the barrier that keeps outside separated from inside - Cholesterol : • Made in the liver • Absorbed from foods (aimal fats- egg, meat, avocado) • Important to membrane integrity • Bad only when there’s a lot of cholesterol attatched to lipoproteins - Fatty acids: Essential (need it from food) and nonessential (available in body) - Essential: Omega 3 (anti inflammatory) Omega 6 (proinflamatory
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