Genetics? Cousins? Relation?

Question

how far down the line until one person is no relation AT ALL i mean to have none of the same family genetics as another of the ancestors family.

please explain in cousin way/grandparent way/ or any other way you can think. thankz :D

Answer 1

This is actually a rather tricky question to answer because there are so many factors involved, including the definition of relatedness (whole genes or the base pairs), random chance, and our limited knowledge of the human genome.  However, with a little math, it is possible to figure out some ballpark figures.

The haploid human nuclear genome is approximately three billion base pairs long.  Because we have two sets of chromosomes, though, this really means that we have around six billion base pairs.  If you assume that everything goes perfectly with no mutations and so on, exactly one-half of the base pairs get contributed to the next generation.  This continues with each subsequent generation.  Thus, if you halve the initial six billion base pairs repeatedly, you ultimately approach a fractional number, and because you can't have fractional base pairs, this would be the end of the line for relatedness.

I just performed this calculation, and ultimately, it would take 32 generations for this to happen.  After 32 generations of flawless reproduction and genetic shuffling, a person would no longer have any of the original parents' DNA from 32 generations earlier.

If you look at entire genes, this number of generations required will be considerably less because there are far fewer genes than there are base pairs.  However, it's impossible to derive a good number for that at this point in time because it is unclear just how many genes we actually have.  The haploid genome consists of between 20,000 and 25,000 protein-encoding genes, but this only accounts for about 1.5% of the genome as a whole.  It is unclear just how many non-protein-encoding genes are present in the other 98.5%.

Add to all of this the fact that DNA replication is never perfect,  and the number of generations reduces even more.

Answer 2

it depends on the chance of the chromosomes

so if you know someone is related to you, there is always a chance they will have some of the same family genetics -

i think chances are, if you know they're related to you, they're going to have some of the same genetics

the chances of them having completely different genomes is pretty rare

for cousins, you share i think it's 1/16 the same genes