2005problemset1key win 04

2005problemset1key win 04 - Problem Set #1 KEY BICD 100 W'...

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BICD 100 W’ 04 (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 and below each phenotype given, indicate the genotypes of the parental and progeny plants in each cross: 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 the pea strains used by Mendel, differences in flower color, pea shape and pea color were each controlled by a single gene. Purple flower color was dominant to white flower color, round peas was dominant to wrinkled peas and yellow peas was dominant to green peas. Mendel crossed a true-breeding strain of peas with white flowers and round, green seeds to another true breeding strain with purple flowers and wrinkled, yellow seeds. The resulting trihybrids were then allowed to self-pollinate to produce an F 2 population. a. In the trihybrids, what color(s) were the flowers, and what were the colors and shapes of the peas? Only the dominant traits are seen: flowers are purple, peas are yellow and round. b. What proportion of the F 2 progeny had white flowers and round, green seeds? p(round) = 3/4 p(green) = 1/4 p(white) = 1/4 so p(round, green and white) = 3/4 X 1/4 X 1/4 = 3/64 c. Of the progeny with these phenotypes (white flowers and round, green seeds), what proportion will be true breeding? To be true breeding, an individual must be homozygous for all alleles controlling the traits of interest. p(WW) = 1/4 p(gg) = 1/4 p(pp) = 1/4 so p(WW and gg and pp) = 1/4 X 1/4 X 1/4 = 1/64 Answer: of the progeny with round, green peas and white flowers, 1/3 will be true breeding. d. How would the answers to part a, b, and c be different if the first cross was between a true breeding strain with white flowers and wrinkled, yellow peas and another true breeding strain with purple flowers and round, green peas? No difference!
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This note was uploaded on 09/11/2009 for the course BICD genetics taught by Professor Smith during the Winter '04 term at UCSD.

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2005problemset1key win 04 - Problem Set #1 KEY BICD 100 W'...

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