"Srinivas S"  wrote in message
>
> 1)What then does the 98% [ chimp/human homology] signify? Part
> genes? Do part genes code for any feature?
>
I believe it means that 98% of bases in the human genome can be matched to
identical bases in the chimp genome.
An expressed gene codes for a protein. If there is single point mutation
then one amino acid in that protein will be different (assuming it isn't a
silent mutation). This could have a huge effect on the gene if the amino
acid is in a vital area, such as the binding site of an enzyme, or it could
have almost no effect if it is just in a nondescript structural part of the
protein.
>
> 2)What percentage of identical genes will we find between 2
> randomly selected humans?
>
Mean heterozygosity is about 0.08%, or 1 in 1250 bases. This means that a
randomly selected person, who has two copies of each gene, will have 2 or 3
differences in the typical gene, which is maybe 3000 coding base pairs.
However there is enormous variation - the insulin gene is only about 500 bp
whilst the titin gene is over 100,000 bp.
Also, variations are not evenly distributed. Histones, used to pack DNA, are
very highly conserved, whilst immunogloblin genes are very variable.
I don't know exactly what percentage of genes will be identical.
>
> I assume that 50% number for parent-
> child arises out of meiosis. What about the number for between the
> two parents? If black color for eye is so common compared to blue
> color, does it imply that even between the unrelated parents, the eye-
> color gene is very likely to be identical. Or is it that many non-
> identical genes code for black eye color?
>
It could be either. It is only a few traits which can be linked definitely
to one allele.
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