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This is confusing. "This is how it happened: when you share around 25 percent genetic similarity with someone, that means that either it's your grandfather, unc
by geuis 12y ago
This is confusing. "This is how it happened: when you share around 25 percent genetic similarity with someone, that means that either it's your grandfather, uncle, or half-sibling".
I have half my dad's DNA and half my mom's, so does my sister. So therefore wouldn't we both share 50% of our DNA? If we were brothers it would be closer to 100%. So a half sibling should be the same as a sister in this aspect. I have a half brother too, so we both got 50% of our DNA from our mother. So we are 50% similar, not 25%.
Is my math wrong?
- J_Darnley 12y agoNo, I think your concept of genetics and reproduction is wrong. You receive a random 0.5 of genes from Dad and your sibling receives another random 0.5 from Dad. This means you share 0.25 from Dad.
- lotharbot 12y agoYou got 23 of your mother's 46 chromosomes, and your half-brother got a different set of 23 of your mother's 46 chromosomes. On average 11.5 of those chromosomes will be the exact same ones -- that's 25% of your total DNA. With a full sibling of the opposite sex, you share about 11.5 of your mom's chromosomes (half of the 23 each of you got from mom will be the same) and 11.0 of your dad's chromosomes (11 of 22; you know the 23rd is different), for a total of 22.5 out of 46 which is 49%. If you're both the same sex, you share on average 11.5 of your mom's chromosomes and 12.0 of your dad's chromosomes (11 of 22, and you know the 23rd is the same), which makes you around 51% similar.
- geuis 12y agoAh that makes sense. I knew I was missing something but wasn't sure what. Thanks.