In the eastern mosquito fish (Gambusia affinis holbrooki), which has XX-XY sexde
ID: 212644 • Letter: I
Question
In the eastern mosquito fish (Gambusia affinis holbrooki), which has XX-XY sexdetermination, spotting is inherited as a Y-linked trait. The trait exhibits 100% penetrancewhen the fish are raised at 22°C, but the penetrance drops to 42% when the fish are raisedat 26°C. A male with spots is crossed with a female without spots and the F1areintercrossed to produce the F2. If all the offspring are raised at 22°C, what proportion of theF1and F2will have spots? If all the offspring are raised at 26°C, what proportion of the F1and F2will have spots?
Explanation / Answer
Since it is a Y linked trait, The F1 would have 2 males having spots since the father had it and 2 females that are normal since they do not even have a Y chromosome.
Same could be said for F2 since same combination is attained as the parents.
if all the offsprings are raised at 22, 50% of the population ( the sons) would have spots.
If all the offsprings are raised at 25, out of these 50%, 42% would have spots. So out of whole population of F2, 21% would be having spots.
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