if a set of twins (A) had babies with another set of twins (b), even if it’s at different times.. would the babies (ab) also be identical? or would they come out looking different?
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Well, remember how non twins are diffrent?
So even if the 2 twins somehow were to pass on the exact same genes, their babies would most likely be like siblings rather then twins
Each egg of a female twin contains an essentially random, unique combination of the female parent’s genetics. So each of the female twins’ eggs would be essentially interchangeable because they are each unique from one another but are ALL picking their genetic combos from the same single genetic parent (either of the female twins). Same goes for the speed of the male twins.
Remember, each individual egg and each individual sperm have slightly different genetic payloads than their sisters and brothers because eggs and sperm don’t contain the ENTIRE genetic code of their parent, they contain HALF of it and that half is going to be different than the halves comprising each of the others. So generic characteristics vary among the eggs in the twin females and in the sperm in the twin males, despite coming from the same genetic parents (twins). This will result in at least some differences between children because each received a different combo half from each of their parents.
That being said, lots of genes are dominant and these dominant genes are MUCH more likely to express themselves in most of the twins of the offspring and THIS will result in significant similarities between the children compared to what you would observe in children of non-twin paired parents.
Does that make sense?
All of this is assuming that the twins are identical – meaning they have the same DNA. Fraternal twins don’t share DNA and are no more or less alike genetically than any other brothers or sisters. Though there are some differences in DNA between twins due to mutations and other factors, let’s just ignore them.
Then what you have is two people with identical DNA, making babies with two other people with identical DNA. And that’s exactly the situation that happens if one set of parents make two babies – the same sets of DNA, reproducing twice. And we aren’t identical to our brothers and sisters – we just share some traits with them.
That’s because the DNA that ends up in an egg or sperm cell is a basically random half of the parent’s full genome – the egg and sperm each have half, and meet up to form a whole. And those halves are different between every single egg and sperm cell. I inherited my dad’s dark hair, so did my brother, but my sister is a redhead – she got a different set of hair color genes than we did. I have my mom’s big nose, my brother and sister both have my dad’s smaller nose – different sets of nose genes, coming from the same source.
So a set of babies born from two sets of identical twins would be, genetically, just like brothers and sisters. They’d share half of their DNA on average. So they’d be cousins to each other, but genetically closer than most of us are with our cousins.
It’s exactly like one couple having two pairs of identical twins. The first pair and the second pair won’t resemble each other more than any other siblings.
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