Everything You Need To Know About Fraternal and Identical Twins | Dr. Sarah Finch

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