Do conjoined twins share the same DNA?

I made another thread asking if twins share the same DNA. I found out no matter what twins do not share the same DNA 100%. Now conjoined twins are a different story (I think). If they share the same body (heart, liver) wouldn’t that mean they actually have the same DNA 100%? Anyone know?

Originally posted by Maddogkull
I made another thread asking if twins share the same DNA. I found out no matter what twins do not share the same DNA 100%. Now conjoined twins are a different story (I think). If they share the same body (heart, liver) wouldn’t that mean they actually have the same DNA 100%? Anyone know?

Yes. Conjoined twins are monozygotic, i.e. identical twins, in which the egg doesn't completely divide. They can be aphenotypical, though, expressing the DNA in different ways.

Identical twins do share 100% DNA. Now, stochastic regulation can make their cells behave differently (and be treated differently as time goes on, making their DNA diverge as their life advances), so people can claim it's "not 100%", but it is pretty much.

Identical twins and conjoined twins are essentially the same thing. They do share 100% DNA, but even between cells in the same organism, little regulations and stochastic variances in things like telomerase activity can cause variation.

reply to post by pondrthis


Well from what I heard when twins were born they shared 99.99999% same DNA but never 100%. But with conjoined twins it seems like they are 100%. Thanks for answering my question

I'm an engineer alright? 99.99999% is 100% to me.

Honestly, I don't know the difference.

If you want to call it that (damn you, telomerase), then conjoined twins are 99.99999% alike. But... who freakin' cares?!

There's nothing in this universe that cares between 99.99999% and 100%, except maybe the speed of light.

reply to post by pondrthis


That is nice you are an engineer. Still dosent make it right to say 100% is the same as 99.99999 %. Now you are right they are the same basically. but still not 100% the same. lol

But I am not fighting casue I know what you mean. I just wanted an opinion. Thank you