Title is pretty self explanatory, but how much DNA would half-siblings share if they had the same mother ? I'm asking for a very specific reason. I'm writing a book in which some boxes can only be opened by people sharing at least 50% of their DNA. Like a father and son, for example (I'm no scientist lol, this is fiction, trying to keep things a bit simple but with a solid base). Would a half-sibling be able to open these boxes too ? If someone has any kind of info, wide or precise, I'd be very interested to know what you have to tell :) Thanks !
If we assume you mean 'have identical sequences' by 'share DNA', then half-blooded siblings share over 99% of their DNA. This is because DNA is responsible for everything responsible to make us human, and most of the differences between the various races of human are in under 1% of all DNA.
If, on the other hand, you're only referring to that small fraction of human DNA which isn't consistent in every human, than it's as follows: Full blooded siblings share, on average, 50% of that DNA, assuming that their parents aren't related at all. Half blooded siblings share, on average 25% of that DNA, assuming the parents aren't related at all.