system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do full blooded siblings end up with such varying results from DNA testing?
gpt
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.