00:01
So you're talking about a graduate student asking 10 mutations a to j, and they all have the same phenotype of resistance to pcp.
00:08
Now you did a complementation test.
00:16
The question asks you to figure out, although there are 10 mutations, how many genes has your student identified? so let's look at this concept of complementation test.
00:28
So for example, you have two different genes, a and b.
00:33
A is mutated, b is a wild type.
00:37
But because a is mutated, they combine to have a pcp resistance phenotype.
00:48
Now you have a different mutation, m1 and m2.
00:52
In this case, you can see a, this time is wild type, but b is mutated.
00:59
Again, you have one mutation, and this also cause pcp resistance.
01:06
So you can see, although both mutants, they have the same phenotype, if you look at the genotype, they actually are different because the mutation occurs in different genes.
01:18
So if you do complementation tests and you combine these two individuals ' mutations, and you cross them, you can see that because a plus is dominant over a, and b plus is dominant over b, as a result, you have a combined a plus and b plus.
01:32
Now you have a wild type phenotype.
01:36
So from there, you can see that this is called complementation.
01:40
Mutant number one is able to complement with mutant number two.
01:45
So in this case, we know that a and b belong to two different genes.
02:00
And this also says that if you have a mutant number three, and you have a and b plus, we do not know what the genotype is.
02:15
But if you combine m1 and m3, you can see that because the mutation, or let's say a and a prime.
02:23
So a prime is a different mutation, but it occurs in the same gene as a.
02:29
So m1 and m3, when they combine, they still have a pcp -resistant phenotype.
02:39
And this means that a and a prime, they actually belong to the same gene.
02:45
They are not able to complement with each other...