ps6s_05

ps6s_05 - MIT Department of Biology 7.014 Introductory...

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MIT Department of Biology 7.014 Introductory Biology, Spring 2005 7.014 Solution Set 6 Question 1 You are a UROP studying inheritance patterns in Alligators. Some of your alligators have angry dispositions while some are friendly. You determine that the gene for attitude is encoded by a single locus. You cross true-breeding friendly male alligators by true-breeding angry female alligators and notice that all of the off-spring (male or female) are angry. a. What are the possible modes of inheritance of angry dispositions in your alligators? Autosomal dominant Autosomal recessive Sex-linked dominant Sex-linked recessive b. For each of the inheritance patterns you selected in (a.), cross an F1 generation angry, female alligator with an F1 generation angry, male alligator. What will be the phenotypic AND genotypic ratios of the resulting offspring? Use A to refer to the allele conferring dominant attitude phenotype, and a to refer to the allele conferring recessive attitude phenotype. Autosomal dominant: F1: Aa x Aa F2: (same for both genders) genotypes: 1 AA, 2 Aa, 1 aa (same for both genders) phenotypes: 3 angry, 1 friendly Sex-linked dominant: F1: X A Y x X A X a F2: Genotypes: 1 X A X A , 1 X A X a , 1 X A Y , 1 X a Y Phenotypes: 2 angry , 1 angry , 1 friendly Assume anger is not a sex-linked trait. You notice that oftentimes the angry alligators have long tails while the friendly alligators have short tails. You determine that the short-tailed phenotype is dominant while the long-tailed phenotype is recessive. You want to determine if tail length and attitude are linked. You cross a true-breeding, angry, long-tailed male alligator with a true-breeding, friendly, short-tailed female alligator to get an F1 progeny. You then cross your F1 generation animals and look at the results in the F2 generation. c. What are the genotypes of the parental generation? Use T to refer to the allele conferring dominant tail length phenotype and t to refer the allele conferring recessive tail length phenotype. Male: AAtt Female: aaTT
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Question 1, continued d. What is(are) the genotype(s) of the F1 generation animals? AaTt e. What is(are) the phenotype(s) of the F1 generation animals? Angry, short-tailed f. What ratio of phenotypes do you expect to see in F2 generation if the traits are not linked? 9 Angry, short-tailed; 3 angry, long-tailed; 3 friendly, short-tailed; 1 friendly, long-tailed g. What ratios of genotypes do you expect to see in the F2 generation if the traits are not linked? 1 AATT, 4 AaTt, 2 AATt, 2 AaTT, 1AAtt, 2 Aatt, 1 aaTT, 2 aaTt, 1 aatt
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This note was uploaded on 11/11/2011 for the course BIO 7.012 taught by Professor Lander during the Fall '10 term at MIT.

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ps6s_05 - MIT Department of Biology 7.014 Introductory...

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