Traditional gene mapping has been applied successfully to a variety of organisms including yeast, fungi, maize, and Drosophila. However, human gene mapping has only recently shared a similar spotlight. What factors have delayed the application of traditional gene-mapping techniques in humans?

Video transcript

Hi everyone. Let's look at our next question. It says bloom syndrome is characterized by pre natal and post natal retardation of growth, great sensitivity of the facial skin to the sun immune deficiency and abnormal behavior patterns, It is caused by a mutation in the blm gene located on chromosome 15. Which of the following is elevated in Bloom Syndrome. Well, the BLM gene we can recall is involved in the synthesis of the pro a hell a case protein. And as we can recall from learning about DNA replication, um this is unwinds the double helix as part of the DNA replication process. So the BLM mutation of LI L. M. Gene causes problems with the DNA replication. In particular, it causes an increase in the exchange of material from sister chroma tides. And it's thought that perhaps the reason of this is that this exchange is in response to access D. N. A damage that's occurred during DNA replication. And since those healing cases are such an important part of that DNA replication process, they sort of help to stabilize the entire process. So the disruption to the replication process results in increased DNA damage and the body sort of tries to repair that by having increased exchange of material between the sister chroma tights. So let's look at our answer choices here and we see that choice a right away is frequency of sister chromatic exchange and that is our correct answer. Um interestingly it also increases the amount of recombination. So exchange of material between uh the paired chromosomes from the two parents. So not only exchange between the sister chroma tides, but between the two different chromosomes from the two different parents. So, involved in both of those similar processes. We'll just take a quick look at our other answer choices. Choice B says the number of genes in the chromosomes. Well, this doesn't change there the same number of genes. You just have more frequent exchange of materials. Choice ceases the number of non functioning genes. Again, no effect on that. Um And Choice D. The D. N. A content in the chromosome. Uh No, that's not what it cause. It doesn't increase the DNA content. It just causes an increase in the amount of exchange of material between sister chroma ticks. So, again, which the following is elevated in bloom syndrome. Choice. A frequency of sister chromatic exchange. See you in the next video.