00:01
In order to answer this question let's talk about inheritance.
00:02
This question says your scientist has a disease which is a recessive trait in humans in a population of 200 people.
00:09
So you have a total of 200 people 75 are homozygous dominant means let's use the aging so homozygous dominant are gonna be 75 then you have that 100 are gonna be heterozygous and the remaining 25 are gonna be homozygous recessive and then they are asking us what is the frequency of the dominant allele the frequency of the recessive allele and the frequency of the heterozygous genotype, okay, so first let's answer question c.
00:39
Okay, because it is easier here the frequency of the heterozygous genotype you have the number of heterozygous genotype okay, it is not the same as the frequency you have the number but if you want to find the frequency you just have to divide by the total amount so in this case you have 100 divided by 200 and this is going to be equal to 0 .5 so this is the frequency for the heterozygous genotype now they are asking you to find the frequency for the dominant and for the recessive allele so in this case you have that p plus q is equal to 1 remember, okay where p is the frequency for the dominant allele and q is the frequency for the recessive allele you also have that p squared plus 2pq plus q squared is equal to 1 where p squared is the frequency for homozygous dominant 2pq is the frequency for heterozygous and q squared is the frequency for homozygous recessive so in this case you you have that the homozygous recessive is 25 okay, but let's let's first convert all of this to frequencies.
01:42
Okay, like we did here for example, the frequency for heterozygous is going to be 0 .5 100 divided by 200 remember, okay then you have 25 divided by 200 and this is going to be equal to this is going to be 0 .125 and finally the same for this one here 75 divided by 200 and this is going to be equal to 0 .375 like this now now in order to find the frequencies you have to replace these values here.
02:21
For example for homozygous dominant you have 0 .375 for homozygous recessive you have 0 .125 okay, but the how well you have 0 .375 for dominant alleles only 0 .125 for recessive alleles only and the heterozygous you have that half of them are going to have dominant alleles and the remaining half are going to have recessive alleles so you have to divide 0 .25.
02:48
That is a freq or i'm sorry 0 .5 that is the frequency for the heterozygous by 2 and you have that it is 0 .25.
02:56
So you have to place 0 .25 here with a dominant alleles and 0 .25 with recessive alleles...