In certain salamanders, the sex of a genetic female can be altered, changing her
ID: 141851 • Letter: I
Question
In certain salamanders, the sex of a genetic female can be altered, changing her into a functional male; these salamanders are called sex-reversed males. When a sex-rever male is mated with a normal female, approximately 2/3 of the offspring are female and 1/3 are male. Given this observation, which of the following statements is most likely to be true for these salamanders? O O O O O They exhibit genic sex determination. Males are the heterogametic sex. Females are the homogametic sex. They exhibit hermaphroditism. Females are the heterogametic sex How do you explain the results of this cross? O The female parent had two Z chromosomes. O The sex-reverse male parent had two W chromosomes. O Both parents were ZW and WW offspring did not survive. O The sex-reverse parent was zz, the female parent was ZW, and ZW offspring did not survive.Explanation / Answer
Ans)1d) Females are the heterogametic sex.
Ans2)c)Both parents were ZW and WW offspring did not survive
Explanation
The sex-reversed male has the same chromosome complement as normal females. If females are homogametic (ZZ), then matings between sex-reversed males(ZZ) and normal females(ZZ) must result in all ZZ female progeny, with no apparent reason for embryonic lethality. However, if females are heterogametic(ZW), then ZW(sex-reversed male) crossed to ZW(normal female) results in 1/4 ZZ(male), 1/2 ZW(female), and 1/4 WW(embryonic lethal). The net result is 2:1 ratio of females to males
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