Variations in a Population

[gmacrider]

Surely not all heritable variations in a population are caused by mutation, are they? I'm slightly different than my brother for example - different eye colour, different nose, much better looking, etc. What is the correct term for the cause of this type of heritable variation?

 

Are there other causes of heritable variation?

[Hellbender]

Are there other causes of heritable variation?

AFAIK, heritable variation is the essence of mutation, but mutation can result from a number of things, most commonly as DNA "copying errors".

[Mokele]

Yes and no. Technically, all different alleles must have arrisen by mutation at *some* point down the line. However, individuals may have heritable phenotypical variation due to interactions between alleles.

 

For instance, say we have a population of mice with two alleles for coat color, B and b. BB mice are black, Bb mice are grey, and bb mice are white (incomplete dominance). If two Bb mice mate, they'll have offspring of all different colors. In one sense, this variation is just caused by the shuffling of genetic information, especially when there isn't complete dominance and genes or alleles interact. However, in another sense, the only reason that more than 1 allele exists is because at some point (possibly in the far distant past), a mutation occured. So it all depends on how far back you want to go.

 

There is also a growing body of evidence that you also inherit certain protiens from your parents which regulate gene activity. In a sense, these protiens produce heritable variation that isn't directly coded in DNA. Of course, the protiens themselves are coded for, and the entire system did at one point arise from mutation.

 

So it really depends on how far back you want to go. Ultimately, all allelic differences stem from mutation, but differences in phenotype between parents and children can be due to simple shuffling of genetic material rather than mutations occuring within that generation. There's a lot to be said for the shuffling of genetic material even without mutation. It confers such a high advantage that it even justifies the arduous, complicated, risky and expensive process of sex.

 

Mokele

[gmacrider]

Thank you Mokele, for that excellent explanation.