00:01
In seals, the gene for whiskers length has two alleles.
00:04
The dominant allele, capital w is long whiskers and the recessive allele, lowercase w is short whiskers.
00:12
The expression of the trait is based on simple or complete dominance.
00:18
So complete dominance, that means that if there is at least one dominant allele, then that dominant trait is going to show.
00:33
Okay, so then if a homozygous dominant, homozygous, meaning, same allele, female mates with a heterozygous male, heterozygous meaning different alleles, what percent of the offspring can be expected to have short whiskers? so i'm going to do a punnet square to help answer this question.
00:55
And first of all, we have a homozygous dominant female, so homozygous meaning the same allele, so that means she's got two dominant alleles.
01:05
And then we have a heterozygous male, heterozygous meaning different alleles, so that means, so he's got one dominant and one recessive.
01:14
So then we finish out our punnet square, each offspring, getting one allele from each parent.
01:23
So then i ask what percentage of the offspring can be expected to have short whiskers? short whiskers is lowercase w and it is recessive.
01:36
And once again, based on our definition, complete dominance.
01:39
If there's at least one dominant allele, then that dominant trait is going to show.
01:43
So that means in order for our recessive short whiskers to show both alleles have to be recessive.
01:52
So looking back at our punnet square, in order for these short whiskers to show, we need the genotype homozygous recessive.
02:02
So both recessive alleles, two little ws.
02:06
Looking at our punnet square, we do not have that.
02:10
Every offspring has at least one dominant allele.
02:14
And that is thanks to this parent here.
02:17
This parent here only has a recessive, i'm sorry, this parent here only has a dominant all of the offspring.
02:24
So every offspring of this parent is going to have at least one dominant allele...