Question

(genetics)

I'm interested in genetics and I've read some articles about the genetic mutations of Drosophila megalonaster vinegar fly. I already know that its livespan changes due to the temperature and the mutations are also caused by a temperature different than normal. So my question is: How exactly does the temperature affect the production or the lack of genes?

Answer 1

I acturlly don't think that temperatures is affecting the genes (at least not in the temperature scale you are thinking about, as a DNA duplex's melting point depends on the length of the DNA molecule and already after 18 nucleotides we are close to 50\(^{\circ}\)C for a two state model), it could be zippering, but I still think you would require a way larger temperature difference.

No I think the "mutation" is found in the gene product, in this case a protein, which we have experienced can denature way before DNA and RNA melts. By doing for example multiple substitutions of key amino acid in the protein stabilizing the native folded state, one could imagine that at low temperatures the protein would unfold, becoming inactive, and thereby changing the phenotype.

So to recap:
If you got a protein who has been mutated in the key amino acids stabilizing the native folded state then lowering the threshold for the denaturation we could imagine the following in terms of phenotyope:
*If you keep the temperature below the threshold for protein denaturation, the phenotype will be wild type
*If you increase the temperature above the threshold, the protein denature, resulting in altered phenotype.

Now one could argue that this argument collapse, if we talk about the cold temperature mutations, but it turns out, if you solve the thermodynamic equations in terms folded vs unfolded state you get 2 points where \(\Delta G=0\), aka we got a cold unfolding temperature and a hot folding temperature.

Answer 2

Another mechanism could be that the increased temperatures changes the populations in the different energetic states (as according to the Boltzmann distribution) allowing a higher probability for mismatch. But again this option require unusual high temperatures and we are again way above 50\(^{\circ}\)C. Also the mismatch would tend to be kind of random in producing phenotypes.

I'm prity confident the protein denaturation model is to be the mechanism. I just found it more funny to guess and use biochemical intuition instead of looking up an article dealing with the mechanism for temperature-sensitive mutations.

Answer 3

@frostbite thank you :) i'll have to check the dictionary to get the rest of your reply (English isn't my native language) but the part that I understood already helped me a lot