Suppose crossover occurs between the homologous chromoso...

Question

Suppose crossover occurs between the homologous chromosomes in the previous problem. At what stage of M phase do alleles D and d segregate?

Accepted Answer

Welcome back, everyone. Let's look at our next question. During meiosis homologous chromosomes can exchange genetic material through crossover events. How does this process contribute to gene genetic diversity? Choice? A? It creates new combinations of alleles. Choice B? It creates new mutations in the genes. Choice C, it eliminates weaker alleles or choice D all options are correct. So let's think about our answer. Choices. Remembering that we do have that possibility that all the options are correct. We're talking about crossover events and how they contribute to genetic diversity. Well, to envision crossover events and their results. We'll imagine an organism. Here's their two um copies of a gene, one from one parent and one from the other parent. So let's say from one parent, they've inherited two dominant alleles, big A and big B. So two dominant alls And from the other parent, they've inherited two recessive alls little a and little b. Now, without any crossing over when this individual reproduces, there are just two types of gametes that can be produced, big A Big B together or a little A little B together, producing the same combinations that this individual had as a heterozygote that its parents had. If however crossing over occurs, there are two additional types of gametes that this individual can produce big, a little bee or little a big B. So in this case, one dominant and one recessive And then one recessive, 1 dominant. So this is a new combination of all the end result being the offspring will have a greater number of possible genotypes than if there were no crossing over. And of course, what is genetic diversity? A greater number of genotypes in a population. So we see here that the way crossing over contributes to the genetic diversity is by creating new combinations of all different from the combination found in the parents. So choice A is definitely correct, but I'm just gonna mark it with a little dot Rather than selecting it because we have to look at our other answers. Since we have that choice D choice B says it creates new mutations in the genes. Well, this is not correct. There isn't any mutation occurring just recombining of and swapping of bits of a chromosome, not changes to the chromosome itself. So choice B is not correct. And at this point, we can therefore eliminate choice D, all options are correct. And then choi says it eliminates weaker alleys. Well, weaker alley get eliminated when the weaker alley causes less fitness to an individual. So that individual is less likely to reproduce. And that all gradually gets weeded out of the population. But it's not a result just of crossing now. So choice C is not correct. So we can go ahead and say for sure that our answer is choice A. How does this process crossing over contribute to genetic diversity? And that is choice A it creates new combinations of alls. See you in the next video.

Suppose crossover occurs between the homologous chromosomes in the previous problem. At what stage of M phase do alleles D and d segregate?

Key Concepts

Crossover

Meiosis

Segregation of Alleles

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