How to expect Twins
Everything You Need To Know About Fraternal and Identical Twins | Dr. Sarah Finch
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oh hello hey I'm just finishing up some
work here but I'm so excited you're here
today we get to talk about something
that's near and dear to my heart which
is genetic I'm so excited that you're
here with me today we're going to talk
about genetics but specifically about
twins and twins are really fascinating
and most people are fascinated and want
to talk to parents of twins about their
twins so they approach them with
sometimes very interesting questions but
sometimes ill-informed questions so my
goal is to educate you so the next time
you talk to a parent of twins you can
impress them with your knowledge so
we're going to talk about the difference
between identical and fraternal twins
and with identical twins they're called
monozygotic so monozygotic mono meaning
one means that one zygote is formed with
fraternal twins fraternal twins are
dizygotic Don's daya means two so two
individuals I goats are formed so let's
look at how that happens
so this is the egg here and this is our
sperm and you can see the sperm is very
small compared to our large egg and if
we were to look in the microscope you
would see that a human egg is very very
large and human sperm is very very tiny
that's because the egg carries all that
good information and what the sperm
brings is the genetic information which
is all it needs to bring so with your
monozygotic twins what happens is one
sperm fertilizes this one egg now in a
normal situation this would then go down
into the uterus and then we would have
gestation for about nine months and then
a baby would be born that's how most
individuals are born one at a time but
in this case the special case of
monozygotic twins or identical twins
this one zygote then slit into two
individuals so now we have two
genetically completely the same
individuals these are essentially clones
genetically of each other they both
travel down into the uterus and gestate
for about nine months and you're born
with two individuals that are going to
be boy boy or girl girl you can never
have a boy girl set of identical twins
because they have to have the same genes
the XX for girls and the XY for voice so
these are your identical twins with
identical twins these are pretty rare
there's actually no known cause
scientists aren't sure why this happens
it's just an extra set of cell divisions
that happens and it's about one in every
250 births that this happens so it's
just a random chances this will happen
anytime there's a fertilization event so
no reason for that but when we look at
ternal twins fraternal twins again
dizygotic so to zygotes or to eggs are
going to be ovulated at the same time
for the mother and that is unusual
usually filling one at a time so in this
case we have two eggs from a hyper
ovulating mother and then we have two
sperm from the father you can see that
they're different colors because they're
different genetically so these
individuals have their own genes they
are not clones of each other they're
actually no more related than normal
siblings who are born years apart so
these are your dizygotic twins so these
can be again boy boy they could be girl
girl or they could be girl boy because
they are unique genetically the odds of
this are going up dramatically so since
the 1980s the amount of multiples not
just twins but triplets and quadruplets
have gone up due to all the fertility
treatments that people earned are going
but actually twins without fertility
treatments occurs for multiple reasons
so there are certain populations that
have higher incidences of fraternal
twins so older mothers are more likely
to have fraternal twins populations from
Africa are more likely to have fraternal
twins as well and the mother who is
going to have fraternal twins it's
called a hyper ovulating mother and she
inherits that that is a genetic thing so
there are specific genes now that we
know you can pass on in the maternal
line to that mother to allow her to all
eight more than one egg at a time so it
is something that you inherit and that's
what the mother in here this has nothing
to do with the father specifically so
the mother house ovulate this to expert
same time so again when we look at this
this is your dizygotic twin so those are
fraternal twins these are your identical
twins and again those are mono zygotes
so the next time you see some twins with
their parents out and about you can come
up to the parents and say number one
you're doing an amazing job because you
have a very hard situation with multiple
kids at the same times you're amazing
right but also then you can impress them
with your knowledge you can say hey if
you have a girl girl or a boy boy you
can say are they monozygotic and they'll
say what and you'll say identical are
they identical and they'll say yes or no
based on whether or not they know that
now the only way you can tell that is by
doing a DNA test which can easily be
done if you see twins that are boy-girl
you can automatically know that they are
dizygotic and
you can tell their parents hey your
dizygotic twins are adorable right so
twins they're amazing fun to talk about
with genetics and definitely not scary
