00:01
So you're doing an experiment with the fruit fly, and in the p generation, you cross two true breeding flies.
00:07
The female parent is brown and windless, and the male parent is black with normal weight.
00:12
All of the flies in the f1 generation are brown and normal wing.
00:16
Diagram the genotype of p and f1.
00:20
So you know there are two genes involved in this case.
00:24
So let's say the color is going to be.
00:31
B, so capital b stands for brown, and black is going to be recessive, lower b.
00:46
Now, you also have a wing, a normal wing is capital n, and lower n stand for the windlass.
01:06
We decided that the brown is dominant and normal wing is dominant because all f1 generation are brown and normal wing.
01:17
So that means brown and normal wing are dominant alleles.
01:21
So since parents are both true breeding, let's say, for parent generation, the female parents is brown wingless.
01:34
So the genotype of the female is going to be true breeding, homozygars, kaptobie, and homozygars lower end.
01:43
And then this is the female.
01:45
And then the male parent is black with normal wing.
01:56
So for a male parent, the genome type is going to be homozygars lower b and homozygars capital n.
02:08
Okay, so now we figure out the parent generation.
02:12
Let's take a look at f1.
02:14
So for parent to produce gametes, since both all the same, so the brown windlass parent, only produce one type of gamete.
02:24
One is capital b and then lower n.
02:28
And for the black normal wing parent, it produced also one type of allele, lower b and capital n.
02:36
So you can see that f1 has a genotype of capital b, lower b, capital n, lower n.
02:46
So this is a heterozygous for both gene, and then brown versus normal wing, this is the phenotype.
02:52
So from this, we can, again, confirm that the brown and brown is dominant, black is recessive, normal wing is dominant, and the windlass is recessive.
03:03
So this is brown versus normal wing.
03:10
Okay, so now we already decided the genotype of p and f1.
03:15
Let's take a look at the first question.
03:18
You crossed f1 back to true breeding wingless fry and count 16 offspring in f2 generation.
03:25
If the wing and color traits are tightly linked and no recombinant occurred, you would expect to count how many.
03:33
So as you can see, f1 generation will produce four type of allele according to mendel's law of segregation and independent assortment.
03:45
So you can have capital b, capital n, and capital b, lower n, lower b, capital n, lower b, capital n, lower b, capital n, lower b, and lower b, lower b, and lower b, lower b, and lower b, lower n.
03:59
Now, a test cross with a black and wingless fly.
04:06
So the other parents is going to be the homozygous lower b and homozygous lower n, black and wingless.
04:15
So this only produced one type of allele which is b and n.
04:21
So now we can actually figure out the f2.
04:26
So we can see for each gamies from f1 is going to pair up with an allele from the black and wingless flag.
04:35
So you have capital b lower b capital n lower n or capital b lower b lower b lower n or lower b homozygars capital n lower n in the last case homozygars lower b homozygars lower n now so you have four different genotype from f2 and then they have the phenotype of brown normal so this one is brown wingless the next one is black and normal wing the last one will be black and windless and the ratio of these four phenotype and genotype is one versus one versus one versus one because each gamete has the same chance of being inherited to the next generation so that means there are four type of gametes each has one fourth a chance so this means each of the four uh the f2 generation has one fourth of the chance to have this particular phenotype so we know all four phenotype should have to have the one to one to one ratio now you have a total of 1600 offspring so this means each one will have one force of the chance 400 you expect to see 400 of brown normal and you have again 400 of brown wingless and you would have 400 black and normal wind black windless flight...