00:01
Have a cell that you have two homologous chromosomes in it.
00:03
One has dominant allele capital nb.
00:07
The other has recessive allele lower n and lower b.
00:11
So there is a crossover event happened between the capital a and lower a, capital b and lower b in this case.
00:21
So as you can see that after the late prophase i and metaphase i and anaphase i, that's what it looks like.
00:28
I'm going to skip the middle part and then draw what's happening in the anaphase one.
00:34
So you can see the two homologous chromosome start to separate during anaphase.
00:43
And you'll have a unique lower a because this is the result of crossing over.
00:55
And then the other one is the opposite, capital a, lower a.
01:05
And then you have lower b and lower b.
01:08
So now you can see that that's the separation of the homologous chromosome, which is the most important feature of anaphase i.
01:19
The two homologous chromosome, one from father, one from mother, they will separate from each other.
01:24
And that goes into each of the daughter cells.
01:27
So at the end of meiosis i, you'll end up having two cells, so two daughter cells.
01:39
One has the black, one get the black, capital a, b, lower a, and capital b.
01:52
And then the other one is the opposite.
01:54
You get capital a, but the rest of them are red.
02:06
So you have b, lower b, lower b, and lower a here.
02:10
So now you can see this is the end of meiosis i.
02:20
So now it will go through another round of cell division.
02:23
And so at the end of the meiosis ii, you'll end up having four different gametes, which are haploid.
02:30
So the question asks you to draw the chromosome diagram of the four different type of gametes that would result from this crossover event.
02:38
Label alleles on each chromosome when you draw.
02:41
So this basically tells us what's going to happen after the meiosis ii is over.
02:48
So during meiosis ii, the two sister chromatids will separate.
02:52
So you can see that the two copies of the same chromosome, we call it sister chromatids.
02:59
They used to be identical in the beginning of the meiosis, but due to the crossover, they are no longer identical.
03:06
The allele capital a and lower a, they switch.
03:10
So that's why you have a chimera with mostly black with a red sequence from the other homologous chromosome.
03:17
So as you can see, now you have sister chromatids that are not identical.
03:22
And the same thing, these two are called sister chromatids.
03:25
Again, due to the crossover, they are no longer identical.
03:29
Now during meiosis ii, the two sister chromatids will separate from each other.
03:32
So as a result, each of the two cells will divide into two more...