Microsatellites are currently exploited as markers for paternity testing. A sample paternity test is shown in the following table in which ten microsatellite markers were used to test samples from a mother, her child, and an alleged father. The name of the microsatellite locus is given in the left-hand column, and the genotype of each individual is recorded as the number of repeats he or she carries at that locus. For example, at locus D9S302, the mother carries 30 repeats on one of her chromosomes and 31 on the other. In cases where an individual carries the same number of repeats on both chromosomes, only a single number is recorded. (Some of the numbers are followed by a decimal point, for example, 20.2, to indicate a partial repeat in addition to the complete repeats.) Assuming that these markers are inherited in a simple Mendelian fashion, can the alleged father be excluded as the source of the sperm that produced the child? Why or why not? Explain.

Video transcript

Hi everybody. Let's take a look at this practice problem together. Which of the following claims concerning microsatellites is correct in the context of paternity testing. So, paternity testing is determining the father and recall that microsatellites are short, repeated DNA sequences that usually occur in a row in non coding areas of our DNA. So let's review our options. We've got a micro satellites are single nucleotide polymorphisms. SNPs that are employed to establish paternity. We can immediately eliminate this option because we know that microsatellites are not single nucleotides. There are several nucleotides that are repeated in a row. So A. Is incorrect. Now we're going to discuss C. Microsatellites can only be used to determine maternal lineage and not paternity. This is also wrong. And the reason why is that microsatellites are found in human genomes regardless of sex. So they can be used to determine both paternal and maternal lineage. So C. Is wrong now, D microsatellites are long, complicated D. N. A sequences that are difficult to interpret. We know that they are not long and they are not complicated. Therefore D is also wrong. So the correct answer is option B. Microsatellites are short repetitive DNA sequences found all across the genome and these DNA sequences are located in thousands of locations on chromosomes. They are polymorphic markers, meaning that they vary greatly amongst individuals because they have high rates of mutation and this is what allows paternity testing to distinguish between individuals. So B is the correct answer. Alright, everybody. I hope you found this helpful and I'll see you soon for the next practice problem