Tay sachs disease is caused by loss of function mutation in...

Tay-Sachs disease is caused by loss of function mutation in a gene on chromosome 15 that codes for an enzyme. The disease is an inherited autosomal recessive condition which is found amongst Ashkenazi Jews of Central European origin. In this population, 2 in 4,900 children are born with the disease. What proportion of the population in the next generation would be carriers (heterozygotes) for this disease?

Transcript

00:01 During genetics, where we are starting with a population, we're told, is 4 ,900 individuals.

00:06 So of those individuals, we know that 4 ,898 show the dominant trait, while only two show the homozygous recessive trait.

00:18 So based on this information, we can do a bit of math to figure out allel frequencies and genotypic frequencies.

00:26 So we're going to start by looking at the piece of information that helps us out the most, and that is this right here, because this is the only one that tells us how many individuals have a certain genotype.

00:38 So we know that two out of 4 ,900 will have the recessive genotype.

00:46 So if you do that math, 2 divided by 4 ,900, you find that the frequency of homozygous recessive genotype is 0 .0041, very small number, which is to be expected when you have only two out of almost 5 ,000.

01:08 But with that, we can start to figure out allele frequency.

01:13 So if i know that having two recessive a's is this frequency, then i can just take that number and find the square root of it to find the frequency of only having one recessive allele or just that one recessive allele.

01:33 So do that, plug that into your calculator, and you end up with a still small but less tiny decimal number of 0 .02.

01:46 And so this is the frequency of the recessive allele.

01:49 Now we can use one of the hardy -weimberg equilibrium equations, which tells us that p plus q equals 1, or the dominant allele, frequency of the dominant allele plus the frequency of the recessive should equal 1 or 100%...

Question

Please give Ace some feedback