How do full blooded siblings end up with such varying results from DNA testing?



How do full blooded siblings end up with such varying results from DNA testing?

In: Biology

A child will inherit 50% of each parent’s DNA. 50% of the mother, 50% of the father. But each child will not receive the *same* 50% from each parent. The genetic code that is passed on is random, every time.

So, let’s say one parent has a small amount of African ancestry in their blood. They have a child, which inherits 50% of their genetic code at random. That small percentage of African ancestry is passed on to them by chance.

But when that parent has another child, the 50% they inherit is different to their sibling, so it’s entirely possible that they don’t inherit any of the trace amounts of African genetics at all.

This is how two siblings can produce different genetic ancestry results.

The DNA that you got from both parents is different than the DNA your siblings got from them.

**Why?** (Optional)

Meiosis, the cellular-reproduction process that makes gametes (sperms and eggs), makes each sperm and egg unique.

Our ancient, ancient ancestors (some of the first animals to exist) were trying to make sure that every baby was born different, and therefore would have a different chance at survival. You wouldn’t make the same baby over and over again if it kept dying, right? But your body has no way of knowing it’s doing that, so it makes sure that every gamete it makes is going to be different in some way.

So, in siblings, the differences can be as small as different eye colours. It doesn’t change your survival chance, but your body is doing it as if it does.