In Drosophila, a cross was made between females—all expressing the three X-linked recessive traits scute bristles (sc), sable body (s), and vermilion eyes (v)—and wild-type males. In the F₁, all females were wild type, while all males expressed all three mutant traits. The cross was carried to the F₂ generation, and 1000 offspring were counted, with the results shown in the following table. Phenotype Offspring sc s v 314 + + + 280 + s v 150 sc + + 156 sc + v 46 + s + 30 sc s + 10 + + v 14 No determination of sex was made in the data. Are there more or fewer double crossovers than expected?

Video transcript

Hello everyone here We have a question telling us given the following parental jammies identify which of the choices shows a recombination resulting from a double crossover. So we have our parental gametes here, their capital E, capital F. Capital G. And lower case E. Lower case F. Lower case G. So let's look at our options. We have capital E. Capital F. Capital G. And lower case E. Lower case F. Lower case G. Because that is exactly the same as our parental gametes. That is just parental gametes. So A is incorrect. Next we have lower case E. Capital F. Capital G. Capital E. Lowercase F. Lowercase G. And as we can see this was crossed over here but there was no other. So that is a single crossover. Next we have capital E. Capital F. Lowercase G. Lower case E. Lower case F. Capital G. And as we can see these here were crossed over. But that's the only one. So that is a single crossover. Lastly we have lower case E. Capital F. Capital lower case G. Capital E. Lowercase F. Capital G. So as we can see we have a cross over here and a cross over here. So that is a double crossover which means our answer here is D. Thank you for watching. Bye.