BIO f325 Summer 2007 - Sample questions - I Exam key

BIO f325 Summer 2007 - Sample questions - I Exam key -...

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GENETICS (BIO f325) SUMMER 2007 Sample questions (I Exam - Key) _______________________________________________________________________ _ 1. (i) In the cross A/a; B/b; C/c: D/d x A/a; B/b; C/c: D/d , what proportion of the progeny are expected to be heterozygous at all four loci? 1/16 (ii). Which of the following are examples of monohybrid crosses? (a) A/a x a/a (b) A/a x A/a (c) A/a;B/b x a/a;b/b (d) A/a;B/b x A/a;B/b (e) A/a;B/B x A/a;B/B (b) and (e) 2. In the following pedigree, (i) Which of the following choices describes the most likely pattern of inheritance? (a) Autosomal dominant (b) Autosomal recessive (c) Cytoplasmic inheritance (d) X-linked recessive (e) Y-linked (f) X-linked dominant (b) (ii) If III-1 and III-2 mate, what is the probability that their offspring will be affected? (Assume that II-1 and II-5 are homozygous for the normal allele) 2/3 x 1/2 x 2/3 x 1/2 x 1/4 = 1/36 3. Complementation analysis of mutants a through f affected in three genes produces the following result, in which (+) represents complementation and (-) represents no complementation. Assuming that all of the missing mutant combinations would yield data consistent with the entries that are known, complete the table by assigning a (+) or (-) sign where these are not given. 1
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b c d e f a - + - - + + b - + + + - c - - + + d - + + e - + f - 4. In terms of genes and chromosomes, explain why two traits might be inherited independently from one another. Also explain why two traits might not be inherited independently from each other. Different traits are controlled by different genes. It is possible that the two genes are located on different chromosomes that segregate independently from one another during Meiosis I. However, if the two genes are located close together on the same chromosome, they will not segregate independently. They may be pulled together into the same gamete more often than not. 5. The gene for yellow body color y in Drosophila is recessive and X-linked. Its dominant allele y + produces wild-type body color. In the following crosses, indicate the phenotype of the male and female offspring. Give the proportion for each phenotype. (i) yellow male x yellow female all offspring yellow (ii) yellow female x wild-type male all females wild-type, all males yellow 6. Suppose that in sweet cherry a single gene controls fruit color [red (R-) is dominant to yellow (rr)] and a second gene controls bloom time [early bloom (E-) is dominant to late bloom (ee)]. A true breeding tree with red fruit and early bloom is crossed to a tree that has yellow fruit and blooms late. The resulting F 1 is selfed to create a population of 500 F 2 trees. The segregation of traits in this F 2 population is shown below:
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BIO f325 Summer 2007 - Sample questions - I Exam key -...

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