A hereditary disease is inherited as an autosomal recessive trait...

Question

A hereditary disease is inherited as an autosomal recessive trait1. The wild-type allele of the disease gene produces a mature mRNA that is 1250 nucleotides (nt) long. Molecular analysis shows that the mature mRNA consists of four exons that measure 400 nt (exon 1), 320 nt (exon 2), 230 nt (exon 3), and 300 nt (exon 4). A mother and father with two healthy children and two children with the disease have northern blot analysis performed in a medical genetics laboratory. The results of the northern blot for each family member are shown here.

Identify the genotype of each family member, using the sizes of mRNAs to indicate each allele. (For example, a person who is homozygous wild type is indicated as '1250/1250.')

Accepted Answer

Hi, everybody. Welcome back. Let's look at our next question. It says, suppose in a marker located from 110 to 175 base pairs, two peaks are generated in the electro heretic analysis graph. What does this result imply? Choice? A, the sample is homozygous for that marker. Choice B the sample is heterozygous for that marker C, the sample had undergone mutation for that marker or D the sample represents the wild type variant. When we look at the results of the electrolytic analysis graph, that is the result of capillary electrophoresis, you look to peaks to determine the number of repeats on a given all. So in this case, if you have two separate peaks, that would represent two alleys with different numbers of repeats. And of course, what is it when we have two alleles of a gene that are different from each other? That's being heterozygous. So our answer here, the result where we see two separate peaks in the region for a specific marker is choice B the sample is heterozygous for that marker. If the sample were homozygous as in choice A, we would see one larger peak to represent that both chromosomes have an alley with the same number of repeats. So I see the sample had undergone mutation for that marker. But we don't know that unless we compare it to some other non mutated version. So we'd need to compare it to its uh its pro it's or excuse me, it's progenitor to see did that marker undergo mutation? But that's not what this result implies here. And finally, choice D the sample represents the wild type variant. Again, we're not comparing it to another sample, which is what you'd need to do. If you wanted to see if something was a wild type variant, you're just looking at the specific number of repeats in this given sample. So that's why choice D is not correct. So again, if we see two separate peaks uh in a specific marker on an electrophrenic analysis graph, this implies that choice B the sample is heterozygous for that marker. See you in the next video.

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