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2008%20problem%20set%201%20KEY - ProblemSet#1KEY...

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Problem Set #1 KEY BICD 100 W’ 08 (L. Smith) 1) . In Mimulus (monkeyflower), plant stems can be either smooth or hairy, and this difference is determined by a single gene, H (call H the dominant allele and h the recessive allele). Examine the results of the following crosses. For each cross, indicate the genotypes of the parents and progeny: cross# parents progeny 1 hairy X hairy all hairy HH HH HH (or one of these parents could be Hh) 2 hairy X hairy 3/4 hairy, 1/4 smooth Hh Hh HH & Hh hh 3 hairy X smooth 1/2 hairy, 1/2 smooth Hh hh Hh hh 4 hairy X smooth all hairy HH hh Hh 2). In rabbits, the difference between normal length fur and a short type of fur called “rex” is controlled by a single gene: rabbits with a dominant allele, R, have normal length fur, and rabbits homozygous for the recessive allele, r, have rex fur. Rabbits with a dominant allele for a fur color gene, B, have black fur and homozygous recessive bb rabbits have brown fur. a. Diagram a dihybrid cross between a black rabbit with normal length fur (homozygous for the dominant alleles of both genes), and a brown rabbit with rex fur. Show the phenotypes and genotypes of the parents and F 1 progeny. BB (black) RR (normal) X bb (brown) rr (rex) ---> F 1 all Bb (black) Rr (normal) b. From a mating between two of these F 1 progeny, what proportion of the resulting F 2 progeny are expected to be. .. black with normal length fur? 9/16 brown with normal length fur? 3/16 black with rex fur? 3/16 brown with rex fur? 1/16 c. From these F 2 progeny, a black rabbit with normal length fur is chosen at random. What is the probability that this rabbit is homozygous BB? 1/3 heterozygous Bb? 2/3 Note that due to the law of independent assortment, fur length has no bearing on the answer. So the answer would have been the same if the black rabbit chosen had rex fur, or if fur length had not been specified. 1
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d. Diagram a cross that could be done to determine whether the chosen rabbit from part c is BB or Bb (assume that rabbits of all genotypes mentioned so far in this problem are available for crosses); indicate what the expected results would be if the rabbit is BB and if it is Bb. Could do testcrosses, as follows:
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2008%20problem%20set%201%20KEY - ProblemSet#1KEY...

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