Genetically speaking, am I more closely related to my individual parents, or one of my siblings, excluding identical twins?
In: Biology
There are chances you have genes, recessive or not, that you do not share with your siblings. They might have been passed to you but not your brother. So, technically speaking, you are closer to your parents. For example. Your mum has blue eyes and round head, and your dad has green eyes and an oval head. You have a round head and green eyes and your sister has oval head with blue eyes. You share with your parents the green eyes (dad) and round head (mum). With your sister you share… nothing! Please note this is a very specific case that is used just for example, you have a lot in common with your sister as well 🙂
You are 50% similar to each of your parents.
You are statistically about 25% similar to each of your non-identical brothers/sisters. It’s a little different if you and a sibling are the same gender, but 25% is an ELI5 generalization.
Your parents.
You have a mix of 50% dad dna and 50% mom dna.
But the genes you take from your mom and the genes you take form your dad are random.
So your sibling is also 50% mom and 50% dad, but it might be a different mix of genes.
This is why siblings can have different hair colors, eyes colors, and in general look really different and be really different.
It’s approximately the same. You get about 50% of your DNA from each parent. This isn’t exactly true in the sense that you, whether male or female or intersex, get all of your mitochondrial DNA from your mother, so you’re getting a little more from your mother than your father in that sense. Plus the Y chromosome is a lot smaller than the X chromosome so that means slightly more DNA from the mom than from the dad if you’re a guy. But still, you’re always getting 23 whole chromosomes from each parent, except in very rare cases, so you have 23 chromosomes from each parent, for a rough 50-50 division.
For siblings, they, too, get 50% of their DNA from your parents. In theory, this could mean you share 100% of your DNA with your sibling (if you’re identical twins). While technically you could also share 100% and not be twins just by virtue of coincidentally getting the same DNA in a totally different egg and spermatozoon, the odds of this are so small as to be impossible. Likewise it’s also in theory possible to share zero percent of DNA with a sibling because the egg and sperm that made them contained all of the DNA from your parents that you didn’t get, but that, too, has odds so small as to be impossible. So on average, you share 50% of your DNA with your sibling. It could be a little bit more, it could be a little bit less.
So while you’re basically guaranteed about 50% of your DNA being from each parent, in theory you could be even more closely related to a sibling if by coincidence the egg and spermatozoon that made them happened to contain a bit more of your same DNA than the 50% that is most statistically probable. Also, if you and your sibling are both boys, then you have identical Y chromosomes, which might push you slightly beyond 50%. If you’re both girls, then you have one identical X chromosome from your father, which can push you slightly greater than 50% similarity. If you’re boy and girl, then you have one whole chromosome each that is completely different from what the other has–Y for him, X for her, and that might push you slightly under 50% as a result.
If you do 23andMe DNA service, you can see this for yourself as it will show how much DNA you have in common with your siblings.
On average it is equal.
You are 50% genetically similar to each of your parents.
You are (some random percentage that is usually close to 50%, and averages out to 50%) genetically similar to siblings.
Depending on that specific number for a pair of siblings they can either be closer to each other than their parents, or vice versa.
If you are talking theoretical, you could even have a genetic twin sibling who wasn’t a twin, or a sibling you shared no DNA with. But those are two extreme ends of a spectrum that the chances of happening are astonishingly small.
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