All language subtitles for 37031x_PR_Human_Mendel_Genetics_09_Define_Phase_v1-en

PETER REDDIEN: Now, I need to explain

phase, which will help you with also figuring out

recombinant and non-recombinant gametes.

OK.

All right, so, if we have an individual

of genotype A little a, B little b,

we want to know which gametes--

sorry, which alleles of these genes

were inherited together from the parent.

So it could had been A and B came together, A and big B,

and little a and little b came together.

It could be that those were the gametes that

produced this individual.

Or it could have been this individual was

produced by those two gametes.

It's the same genotype, but what differs

is which ones came together to produce this individual.

So, when we were doing crosses before in a controlled way

in a lab where we can design them

in a way to know what's going to be the outcomes

or be able to assess and interpret the outcomes,

we could set up crosses where we would know the phase.

So we might do some cross like this

to generate our heterozygous animal that we're

going to be using for mapping.

Because we know the genotype of the parents,

we will be able to determine what the phase information is

in this offspring.

I've defined phase on the screen as the alleles of loci,

like genes or markers, in an individual that were inherited

together from the same gamete.

We know that this big A and this big B allele of those two genes

came together from this gamete and the little a

and the little b gene allele came together from that gamete.

So we know the phase here.

Phase is known.

Now, the problem is, we might look at a pedigree,

and we might not know the phase, either because

of the genotypes involved in the cross

or because there's some lack of information.

We don't have the family history going back indefinitely.

We've got some data to work with.

So we'll have to take this into account

in order to determine if a gamete is

recombinant or non-recombinant.

You can see how that matters.

If it was this configuration, the non-recombinant gametes

are like this.

And, if it was this configuration,

the non-recombinant gametes are like that.

So which configuration these individuals

have will be important for interpreting

whether gametes are recombinant or non-recombinant.