What two essential criteria must be met in order to execute a successful mapping cross?

Video transcript

Hi all, let's look at our next problem. It says in Drosophila crossing over was shown to occur only in females and not in males. The genes for purple eyes and vestigial wing are 10. M. U. Apart on chromosome two determine the number of gametes produced by a female and male Drosophila, both of which have Jenna types P plus P. V. G. Plus V. G. So both male and female are headers I guess for both traits. And we know that crossing over occurs only in females. Now we've seen that are two traits are on the same chromosome. They're not that far apart. But crossing over can occur. And this question isn't asking us how often it's going to occur. It just says, how many different gametes can a female versus male Drosophila produce? So the male is going to be pretty simple since we see crossover does not occur in males. So let's look at our mail situation first. So since the genes are on the same chromosome, if our mail is P plus V. G. Plus and then his other on one chromosome and then P. V. G. On the second chromosome, he can produce two types of gametes. He can produce the p plus V. G. Plus gamut, that's one and he can produce the P V. G. Gamut. There will be no crossing over this and so there's no other um comment there'll be no recombination and no other combinations possible. The female, however, can have crossing over. So with the same the same genotype, she can produce more types of gametes, she can produce the same as the male here. The original linkage that she inherited from her parents, P. Plus, V. G. Plus and P. V. G. But there could be crossing over occurring between those two genes. So that gives her two additional possibilities. She could end up with a P. Plus V. G. And a P. V. G. Plus. So the male can only produce two types of gametes that the female can produce four types. So when we look at our answer choices, we see that choice C. Indeed shows the female producing four and the male producing too. So that's our correct answer to the number of gametes produced by female and male Drosophila, each of which are hetero cygnus. Um For the purple eye and vestigial wing traits. See you in the next video.