00:01
With just one parental generation and an f1 generation with its test cross.
00:04
And then we're going to look at two different examples, one where we see what the f2 generation should look like if the genes are not linked and what the f2 generation should look like if the genes are linked.
00:17
So here the parents, we see that one of them is homozygous recessive at both genes, one is homozygous dominant at both genes.
00:24
So that means that when they give chromosomes to their offspring, the f1 generation, this parent here only has recessive alleles.
00:34
They only have recessive a's, so they have to give a recessive a to all their offspring, no matter, you know, if it's this one or this one.
00:42
And b's are the same way.
00:44
They only have recessive to give, so all offspring have to receive a recessive from them.
00:48
And so that's the chromosome we're going to get from that parent.
00:51
Other parent is similar in that they only have dominant allelial, so all offspring have to receive dominant alleles from them.
00:58
And so altogether our f1 generation is heterozygous, but the alleles come on these two distinct chromosomes, and that's going to be important for this.
01:08
Now we're going to cross the f1 generation with the test cross of being completely recessive, so both alleles, both chromosomes are recessive a, recessive b.
01:18
So when we look at the f2 generation, we can look at whether the genes are linked or whether they're not.
01:25
So whether, you know, if they are not, if they are not, you know, if they are not linked, then we're just going to do the classic punnet square and look at that.
01:36
So if we're doing a punnet square, then we would have to look at the f1 generation and test cross for the possible comedic combinations.
01:43
So for the f1 generation, we could have this a with this b.
01:49
We can have this a with this b.
01:53
You could have this a with this b.
01:57
Or we can have this a with this b.
01:59
And you see here that there are four possible comedic combinations from our f1 generation.
02:05
But when we look at the other one, the test cross for the f1 generation, first a, first b, first a, second b, second a, second a, both, then you see that there are only one possible gamutic combination.
02:29
It is always going to be recessive a, recessive b, because that's all they have to give.
02:33
So we can do a complete 4x4 punnet square for this situation, finding all the possible comedic combinations.
02:44
From these two individuals.
02:46
However, when we do that, we can, you know, looking up and to the left for each probability box, we see that all of the rows are the same...