00:01
So the coloration of guinea pigs is determined by a single gene with two annuals.
00:06
So a guinea pig from a true breeding black strain is mated with a guinea pig from a true breeding white strain.
00:14
The f1 progeny are all black.
00:17
Okay, so first of all, which is dominant, which is recessive.
00:20
Well, for this, we can see that if we cross black and white, we get all black.
00:25
So black is going to be dominant here.
00:27
So let's have a capital b for black and a little b for white.
00:31
So the f0, the parental generation, is true breeding black, so that means homozygous with white.
00:41
And the f1 generation are going to be all heterozygotes.
00:46
Okay, now we can get to the questions.
00:48
First of all, what proportion of the f2 progeny is going to be white? so the f1 cross means two heterozygotes.
00:57
So i'll do a punnet square to show the possible offspring.
01:01
So in the planet square, you have the gametes of the parents along the outside, like so, big b and little b for each parent, and then inside the square we are going to combine them to get all possible offspring.
01:27
So these are the outcomes, and we can see that we have 25 % will get two of the big b allel, 50 % will get one black and one white allele, 25 % will get two white allele.
01:43
And which of these are going to act with you white? well, it's just this square down here.
01:49
Because white is recessive...