In a laboratory population of drosophila, all the males are xsy. among the females, 15% are xixi, 50% are xixs and 35% are xsxs. assuming random mating, what proportion of the male flies in the next generation will be xiy?

a. 12% b. 30% c. 40% d. 65%

2. a virgin female drosophila mates and produces 34 daugthers and 38 sons. 18 of these sons sire only daughters, while the remainder sire approximately equal numbers of daughters and sons. what the gynotypes of the original female and the male with whom she mated

a. xixs and xsy b. xixs and xiy c. xixi and xsy d. xsxs and xiy

3. if the e and f are expressed, the xi chromosome will be prevented from reaching 100% frequency if selection pressure cause which of the following to be true?

a. xsxs flies have the lowest fitness of any genotype b. xsxs flies have the highest fitness of any genotype c. xiy flies and xsy flies have equal fitness d. xixs flies xsxs flies have equal fitness

1A. 40% is The Answer C 2a: A is the answer XiXs and XsY

3a Answer is A

Explanation: 1A. 40% is The

random mating point to the directiojn to Hardy–Weinberg genetics. all males receive a Y chromosome from their fathers, male contribution can be ignored; while we focus on the type of chromosome the females will donate.

assign Xi as p in the H–W equations, and Xs as q. 15% of the females are XiXi

35% are XsXs (35% qq), (15% pp), 50% are XiXs (50% pq) put these values into the H–W equation for genotype frequency

(pp +2pq + qq = 1)

gives us 0.15 + 0.50 + 0.35 = 1; solving for p and q gives us approximate values of p = 0.4 and q = 0.6.

H–W equilibrium state that allele frequency remain constant from generation to generation, males can inherit either Xi (p) or Xs (q), the percentage

of XiY males equal the frequency of the Xi allele: therefore p = 0.4 which is same as 40%.

2A

34 daughters and 38 sons.

18 sons only make daughters, remainder have equal number of each

must be A.

- male must be XsY, or else the 1st gen would ONLY be females

- only half the sons' kids have it so mother must be XiXs

3a.

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