- Okay, so Mendel figured
out that, essentially, somehow,
there have to be discrete things
in these pea plants
that actually separate
or segregate during baby-making,
and that then are recombined
during fertilization.
So, the Law of Segregation
states
that something separates
or segregates
during baby formation.
And let's look at that.
We can actually
make sense of that idea,
because essentially
we can make sense of it--
we can make sense of the idea
because we understand
the genotypes of these plants.
So, we know that the white
phenotype is coded for
by recessive alleles,
and in order to express
the white phenotype,
we have to have two copies
of the recessive allele.
We also know that in a true
breeding plant,
it has to be homozygous.
No matter what happens, we
have to end up
with the same phenotype,
so that it has to be
true breeding.
Now, take a look
at the dominant purple,
this also has to be
true breeding,
it has to be homozygous.
This time, it has to be
homozygous dominant.
Now, tell me, just
take a wild guess,
what do you think is true
about the genotype
of the F1 generation babies?
These babies are going
to be heterozygous,
and that's the idea
of segregation.
These alleles divide, meiosis,
and make gametes,
and then recombine,
fertilization,
to make a diploid
organism again.
That's the Law of Segregation.
The place where you actually
see this in action
is when we segregate
a heterozygous genotype.
And then we see,
and we're going to defend this,
we're going to actually do the
Punnett Square to show us this,
then we're going to see
the actual 3 to 1 genotypic
or phenotypic ratio.
Before moving on, we're going
to do a quick review
of the concept
of Independent Assortment,
and then we're going
to look at a Punnett Square
and hopefully
convince ourselves that, yeah,
Independent Assortment
and segregation are part
of being able
to interpret our babies,
who's out there,
what babies are going to come
out of this possible soup?
