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UM BIOB 272 - Mendelian Genetics Continued

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BIOB 272 1st Edition Lecture 6 Outline of Last Lecture Mendelian Genetics (Transmission Genetics)I. Mendelian Genetics:II. GregorMedel’s (“father of genetics”) Contributions:i. 3 PrinciplesIII. Why garden Peas (Pisum)?-the right organismVI. Experimental Approach1. Self-fertilized plants 2. Crossed two different true-breeding lines3. Self-fertilized an F1 hybrid- Example: Tall (TT)=dominant, Dwarf (Tt)= recessiveIV. Mendel’s Principles1. Dominance2. SegregationV. Mendels’ reasoning in modern termsOutline of Current Lecture Mendelian Genetics ContinuedI. Mendel’s Principles:1. Dominance: 2. Segregation: These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.3. Independent Assortment: II. Mendel’s Experimental approachIII. Example of Independent Assortment IV. Clicker QuestionsV. Mendelian laws of segregationVI. Why is independent assortment important?CurrentLectureMendelian Genetics ContinuedI. Mendel’s Principles:1. Dominance: In a heterozygote, one allelemay conceal another.2. Segregation: In a heterozygote, twodifferent alleles for a single trait segregatefrom each other with equal probabilityduring the formation of gametes.3. Independent Assortment: The alleles ofdifferent genes (or loci) segregate (or assort)independently of each other.*The forked-line method can be used to predict the outcome of an intercross involving threeindependently assorting genes.II. Mendel’s Experimental approach1. Self-fertilized plants to generate ‘true-breeding’lines for each trait =>parental generation (P)2. Crossed two different true-breeding lines=> 1st generation progeny (F1 hybrids)3. Self-fertilized an F1 hybrid=> 2nd generation progeny (F2 hybrids)III. Example of Independent Assortment with Dihybrid Crossing of pea seeds: Seed texture: Round (R), Wrinkled(r) Seed Color: Yellow(Y), Green(y)A. F1 Hybrid: Round, Yellow: YYRR Wrinkled, Green: yyrr=>RrYyGametes: RY, Ry, rY, ry- Complete Linkage-only parental combinations= RY, ry- Independent Assortment-all combinations possible(use all gametes)= RY, Ry, rY, ry**Use a fork diagram to determine gamete types (see lecture slideshow)Answer: 25% RY, 25%Ry, 25% rY, 25% ryB. F2 Hybrid: RrYy x RrYy**Use Punnett Square using RrYy x RrYy on outsideAnswer: 9 round, yellow 3 round, green 3 wrinkled, yellow 1 wrinkled, greenIV. Clicker Questions:1. Albinism in wolves is caused by a recessive allele (a) at a single gene or locus. An albino female mates with a normal male who carries the albino allele (a). What proportion of the resulting offspring would you expect to be albinos?(a) None.(b) 25%(c) 50%(d) 75%(e) 100%Answer:50%2. You toss a coin four times, what is the probability ofthrowing all heads?(a) 1/2(b) 1/4(c) 1/8(d) 1/16(e) 1/32Answer: 1/16 3. TtYyRr x TtYyRr How many gamete combinations are there for this cross (hint: how many squares would be inthe Punnett square)? a) 16 b) 64c) 128d) 8Answer: 644. Dihybrid test cross You have a tall plant with yellow seeds. Whencrossed with a dwarf plant with green seeds (ttyy)you get progeny that are 50% green and 50%dwarf. What is genotype of the tall plant? (hint:25% of the progeny are green and dwarf)a) TTyyb) ttYYc) TtYyd) TTYyAnswer: TtYyV.Mendelian laws of segregation: mechanism1: Alleles at a single gene segregate into thegametes at random (1:1 ratio)2: Alleles at unlinked genes assort independently,so all combinations are equally likely.**Both of these laws result from how homologouschromosomes line up in metaphase ofMeiosis IVI. Why is independent assortment important?- People can make 8,388,608 chromosomally unique gametes-then they are split even


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