Biology Forums - Study Force

Hi guys,

enjoying reading through these posts however i have a problem of my own i could do with a helping hand

I have a question on an article http://www.pnas.org/content/107/5/1815.full (http://www.pnas.org/content/107/5/1815.full)  that i need to comment on in relation to the following question.

The question  is that for  lizards collected from the White Sands habitat, why would the dominant or recessive nature of the light Mc1r allele in fence and whiptail lizard species, ie dominant in the fence lizard and recessive in the whiptail, result in the difference seen in light allele frequency between the two different species.

Many thanks

This is a classical case of convergent evolution. Convergent evolution is when various species evolve similar solutions to similar evolutionary pressures, independently and often at different times. So while both lizards how the Mc1r gene, one species has managed to turn it off (likely via transcription factors), while the other likely required it to be transcribed into protein in order to survive.

Thanks for reply bro, i understand what u r saying but how does that relate particularly to the recessive or dminant allele in the respective species???

Cheers

In the fence lizard, the blanched allele is dominant, its frequency never exceeds 50% in any habitat, and it is completely absent from the dark-soil area. It needs to be dominant in this allele or else it will be susceptible to predation and will not exist over time. Those that were not dominant for this allele had to migrate where it was safe. It needed to produce more melanin so that it could probably camouflage itself (This is my hypothesis, although I'm not 100% sure). In contrast, blanched allele is recessive in the whiptail lizard, it is nearly fixed in white-sand habitats, and it persists at low frequency in the dark-soil region. Therefore, this specifies didn't like have to produce as much melanin in its respected region of inhabitance. Those that were dark were preyed upon whereas those that were white could hide in the sand.

What do you have in mind other than predation?

Thats why im confused, if the light allele is dominant in the fence lizard in the white sands area why is it not present in higher frequencies? I would of thoght it would be 3:1 in favour of the light allele even taking into account slection pressure from predation, conversely the whiptail lizard is present in much higher numbers yet it is recessive in this species - it seems the opposite way round. I think thats what the questions is trying to reason why there isnt the expected 3:1 ratio

In a perfect world, yes - you'd find 3 to 1 but there are always other factors that determine these ratios (i.e. epistasis). You seem very knowledgeable in the field, glad to have you as a member!

Lol i wish i was mate, i just cant figure this one out - even taking into account geneflow, and natural selection pressures it doesnt make sense to me LOL

Hate to say it, but I'm not too sure either :-\. The article, though well-written, doesn't mention anything about sexual selection. Do you think it could have an impact?

Maybe , that was one thought i had that even if the light allele is dominant, the ones with the wild type allele will be more attractive to mates but i dont think it can apply t this particular question as like u pointed out theres no reference in the article to it.

The question is basically asking what s the relationship between the allele being domainant or recessive and the frequency of the alleles in the white sands environment - im stumped to be honest

Thats night shift over - off to bed 8)