maximal GENETIC ancestries

[jrg23]

Hello,

Is it poissible to have the DNA or gene of all ancestries?Because a human has 20000 genes.

And I have 10000 gene of my mother and 10000 gene of my father.

And 5000 of my grandpa and so on.

So lets go 20 generations back: I have 20000/(2^20)=0.02 gene of every ancestor who lived 20 generations ago.

So I lost many gene of my ancestors, right?

The maximum is to have information about 20000 ancestors.

 

Is the way I'm thinking right or wrong?

 

Thank You.<br class="Apple-interchange-newline">

[CharonY]

No, you have the same number of genes as you are ancestors. You will have different allele variants, though. The number of genetic loci is more or less fixed (not entirely true, but for this discussions close enough). You basically fill up the loci with the alleles (i.e. sequence variants at any given locus) from your parents.

[jrg23]

Yes I have 20000 genes and my ancestors too.

But lets take a view on an ancestor 20 generations ago: I have 20000 genes, but (statistical) only 20000/(2^20)=0.2 genes of this ancestor.

I have 1048576 ancestors 20 generations ago and every one had 20000 genes, but I can't have 20000*1048576 genes.

So I can have 1048576 genealogic ancestors, but no more than 20000 genetic human ancestors.

Is this right?

 

Thanks!

[CharonY]

Nope from the 20k genes any number could be identical to a given ancestor 20 generations ago. They do not get (necessarily) outdiluted over the generations. To make a correct guess (using only genes, although non-coding regions are also critical) you would have to know how many variants of a given allele exist in the relevant pool (consisting of your ancestors). If, for instance, in a given locus an only one allele exists within your family, you would have that allele and, assuming that you do not mate with someone who has a variant, so will your offspring.

 

edit: it could be that you are using genetic ancestor in an unusual way and I may misunderstand you.

Edited March 27, 2012 by CharonY

[jrg23]

Have all humans the same 20000 genes and is the only difference the allele?

 

For example Peter has a black father and a white mother and Peter looks only white and Peter will have a white partner and his descendants will also have only white partners. Is it possible that one descendance could look like a black after 30 generations(whith only white partners in each generation) or not? (I know there will be race mixing after 30 generations, but ist is only a theoretic question)

 

Will the descendants after 30 generations still have genetic information of this black ancestry or is the possibility very high that the "black genetic informatin" will be "delated"?