Newby question about genetic

[Jehan]

Hi,

I'am curious about the transmission of dna.
When two parents A and B have a child O ; C and D have a child P
O dna will be 50% A and 50% B ; P dna will be 50% C and 50% D

O and P have a child N
N will be 50% O and 50% P

Can we conclude N is 25% A, 25% B, 25% C and 25% D
OR N can be 20% A 30% B, 10% C and 40% D?

Thanks for the answear

[Jehan]

Nobody answear because there is so much bs in my post, nobody have the answear or you don't get my question?

[Leto]

Hi,

I'am curious about the transmission of dna.
When two parents A and B have a child O ; C and D have a child P
O dna will be 50% A and 50% B ; P dna will be 50% C and 50% D

O and P have a child N
N will be 50% O and 50% P

Can we conclude N is 25% A, 25% B, 25% C and 25% D
OR N can be 20% A 30% B, 10% C and 40% D?

Thanks for the answear
I think the former conclusion is more correct.

[Jana]

It is interesting question. Actually siblings do not get identical results (at least in ancestry painting) but it may be just a miscalculation :D That would mean you can inherit more from one parent...?

[Not a Cop]

It is interesting question. Actually siblings do not get identical results (at least in ancestry painting) but it may be just a miscalculation :D That would mean you can inherit more from one parent...?

I've read about this somewhere in russian, but i can't remember where, but yes you can inhert more from one grandparent than from another.

[igo112]

...

[Stanley]

You're never going to get precisely 25% from each grandparent.

Think of it like this. Everyone has 2 copies of each chromosome, one from each parent. So everyone is exactly 50% related to both of their parents (autosomally). However, a person's offspring will only get one copy of this pair, and which one they get is entirely random. That is, the offspring will receive a random mix of his grandparents' chromosomes.

It's theoretically possible (but practically impossible) that, for example, someone could inherit from his paternal half every one of his paternal grandfather's chromosomes and therefore be 50% identical to his paternal grandfather and 0% identical to his paternal grandmother. Of course that would be the longest of statistical long shots, and it's also made less likely by the phenomenon of crossing over, whereby you don't always inherit a full chromosome from one grandparent but instead one that is a mix of both grandparents' DNA; but it's at least technically possible.

What the normal variation in this transmission is, I'm not sure. I actually made a thread a while back asking people what % of their genome they shared with close relatives on 23andMe because I was curious about this myself. I got one reply from someone who's had a grandparent tested:


I share 33.3% with my maternal grandpa :)

Small sample size, but it looks like it's pretty normal for there to be sizable deviation from the expected 25%.

[Jehan]

Thanks for the answears.

[Prisoner Of Ice]

You could theoretically be 100% identical to any ancestor but it's impossibly unlikely. Females have preprogrammed recombination rate and this is also affected by chance. So you can get any combination of genes from your parents but generally for any specific gene you get one from mom and one for dad. That is why you can wind up with blond hair or some other recessive feature even if only one parent has the gene, but usually you won't.