00:01
What is the probability of parents with the following genotypes, producing offspring with a genotype homozygous dominant? so our first parent is heterozygous for both genes.
00:13
Heterazigis, meaning different alleles.
00:17
So we've got one dominant allele and one recessive for both traits.
00:23
And then we have a parent heterozygous for a.
00:26
So once again, one dominant a, one recessive a.
00:29
And then homozygous dominant for b.
00:33
Homosigas meaning same allele, so both alleles are dominant.
00:37
And then i went ahead and filled out the punnet square to help save a little bit of time.
00:43
And i wrote the possible gene combinations for each parent.
00:48
And then filled out the punnet square, each offspring getting one allele from each parent for each trait.
00:55
So now we are looking for the genotype homozygous dominant.
00:59
And i like to help circle what we're looking for to help me visually see it.
01:04
So we've got this one here.
01:07
We've got this one.
01:10
And then we look through the rest of our punnet square and we don't see that genotype again.
01:15
So therefore, two out of the total 16 offspring will have that homozygous dominant genotype.
01:23
We can reduce that down to 1 8th.
01:27
And then if we want, we can even find the percentage, which is 12 .5%.
01:32
So this here is the probability that these two parents crossing will have offspring with the genotype homozygous dominant.
01:47
Okay, next question.
01:50
In a cross between a female with this genotype and a male with this genotype, what proportion of the progeny will be the same phenotype as a female parent? okay, so when we have a cross that has more than two alleles, i like to do a punnet square for each individual trait, figure out the probability of the trait that we are looking for.
02:14
I'm sorry, for the genotype we are looking for in each trait.
02:18
And then i like to use the probability rule of and to figure out the probability for the full genotype.
02:25
And that probability rule of and is you multiply the probabilities together.
02:31
Because we are looking for an offspring that has this genotype and this one and this one and this one.
02:41
So there's an and between each of those.
02:42
So we're going to multiply those all together...
