00:01
In order to answer this question, let's talk about inheritance.
00:03
This is in pythons, the piebald trait that is irregular patches of pigmented and unpigmented regions is recessive.
00:11
A breeder crosses two normally pigmented pythons who have previously produced some piebald pigmented progeny.
00:18
This cross produced five progeny.
00:20
What is the probability that all of the progeny will have the piebald phenotype? so in this case, they are not specifying but we can suppose that this trait is autosomal.
00:29
Okay, because well, this test can be autosomal or x -linked.
00:32
But in this case, let's suppose that there is an autosomal condition.
00:35
So let's use the a gene.
00:36
You have the dominant allele a and the recessive allele a.
00:39
So you have the homozygous dominant and the heterozygous are going to code for normally pigmented pythons and the homozygous recessive is going to be for piebald phenotype.
00:56
Now it says a breeder crosses two normally pigmented pythons.
01:00
It means like this because you don't know if they are homozygous dominant or heterozygous because both of them code for normally pigmented pythons.
01:09
But it says who have previously produced some piebald pigmented progeny.
01:14
So it means that they have produced some homozygous recessive progeny.
01:18
Remember that an offspring inherited one allele from its parent.
01:21
In this case, one recessive a was inherited from this parent and this recessive a was inherited from this parent.
01:27
So practically both parents must have at least one recessive allele.
01:31
So it means that both parents are heterozygous for normal pigmentation.
01:37
Now the next question says, this cross produced five progeny.
01:44
So you have five progeny.
01:46
One, two, three, four, and five.
01:50
And they are asking you, what is the probability that all of the progeny will have the piebald phenotype? so let's make a square for this cross.
01:57
You have heterozygous and heterozygous.
02:01
You get homozygous dominant, heterozygous, heterozygous, and homozygous recessive.
02:06
So it says the probability that all of the progeny will have the piebald phenotype.
02:11
So it means that you want the homozygous recessive.
02:14
You have a total of four possibilities here.
02:16
In all of these four possibilities, only one is going to be piebald.
02:19
So your probabilities for getting piebald offspring is going to be one quarter.
02:24
And you want the five of them to be piebald.
02:26
So it means one quarter, one quarter, one quarter, one quarter.
02:30
And you want these five events to happen at the same time.
02:35
So you have to multiply all of these events like this...