Each person’s DNA is unique. Sperm carries half of DNA, and eggs carry half, but the mother/father have billions of sperm cells and eggs. What do those sperm cells and eggs have in common? How do DNA test know my parents are indeed my parents? How similar is my DNA with my siblings?
In: 0
You get one set of chromosomes from each parent. You have 23 pairs for 46 total chromosomes. And you always get one of each pair from each parent. Even though everyone’s DNA is unique, 99.9% of it is identical. That .1% is where we look for the differences. The thing is, we have so much DNA that .1% is a lot, so we can compare those small changes to identify parentage.
Humans and chimpanzees share 99% of their DNA, and we are still very different. Humans and bananas share 50% of their DNA, and we are extremely different. We just know where to look for those differences.
I can answer one piece
Sperm has 100% of dad egg has 100% of mom that’s 200%. You only need 100 so you get 1/2 your mom and 1/2 your dad. Your siblings start fresh with the 1/2 of parents. There would likely be some same but not exact unless there’s a twin identical. Even fraternal twins are different mixtures due to new eggs and sperm for each.
Paternity tests are looking for matches the higher the matches the closer you’re related.
The only thing each each sperm or egg have in common with each other is that each will contain half of the DNA of the corresponding parent. The child that results from the union of any given sperm and egg will have half of its DNA from the father and half from the mother. A DNA test will identify certain locations on your DNA (called markers) and depending on how the markers match between you and the parent, will enable the geneticist to estimate a probability that a person is the parent. Your DNA could be the same as a sibling (in the case of identical twins) or much different. The probability of you receiving a completely different is so small (approx. 1 in 7×10^12 ) it is effectively zero. Siblings usually share about 50% of their overall DNA.
Maternity is easiest to prove. Our cells have mitochondria which have their own genetic material and only the egg has them to pass on. So your mitochondrial DNA came from your mother. Mitochondrial DNA can’t tell you if it’s your mom, your mom’s sister or any of the females on your mom’s side as it all would be the same.
If you have a Y chromosome, typically males but there are others, that will only come from the father. So you can match your Y chromosome to your dad and grandpa and uncles from that side.
If it’s neither of these cases, your DNA has 4 main components. In listing they’re typically just G,C, A & T. Dna will be processed and come out as a chain like GCCAGTGACAGTAGCAGATAGACACACAGTAGACAGAT. They will then take the child or parent in question and process it and basically try to match patterns in the sequence. The more the patterns match, the likelier it is that the two are related. Lab reports never REALLY say a yes or no that someone is the father. They give out a percentage that then a professional will use their judgement on to say yes, it is 98% likely that this man is the father.
As for how similar your dna is to your sibling, without processing it you can’t really know. Typically it’s between 25 and 75% similar. In identical twins, it’s typically believed to be 100% but there are cases where it’s reported like 99.9999999999% so it’s just rounded up for simplicity sake.
Edit: fixed where I wrote fraternal twins not identical. I had a moment.
Latest Answers