Re: Why dosage compensation doesnt apply to autosomes?

Dear Rajesh,

To answer your question, let's think about the reason for dosage 
compensation:  Female mammals have two X chromosomes.  Males have only one, 
therefore they are considered hemizygous for all the genes on the X and will 
express the single allele of the X-linked genes that they inherit 
(regardless of whether these alleles would behave dominantly or recessively 
if there were two copies present). Because there are genes on the X 
chromosome that are required for normal cellular function and development in 
both sexes,  it stands to reason that both sexes would use the products of 
these genes in similar concentrations, or "doses".  And, because the females 
have the potential to synthesize twice as much of any product of a gene 
found on the X, the mechanism of  X inactivation has evolved to keep things 
equal between the sexes. 
You state as much in the wording of your original question, but then ask why 
this mechanism doesn’t occur in autosomes.  The simple answer is that, since 
both males and females have the same number of autosomes (2 of each), it 
isn’t necessary to selectively inactivate them to equalize their gene 
expression potential.   

Thanks for writing; please feel free to contact me again if you have further 
questions about this or any other topic.

Warm Regards, 
Jen