1
$\begingroup$

Coming from computer science with an interest in genetic programming (a process emulating evolution) I'm curious about whether the rate of mutation is homogeneous across the whole genome, or if some parts of the genome differ in the rate of mutation.

For example we could imagine, without going to into details that could invalidate the example, that parts of the genome associated with the immune system could have a relatively higher mutation rate, because this would allow for a quicker adaptation to quickly evolving pathogens.

Is there any empirical support for that different part of a genome of some species have different mutation rates, that would give us empirical support for the possibility that some species under evolution have the ability to adjust (by NS itself or even epigenetics) the mutation rate of specific parts of the genome?

Clarification

I'm only interested in the mutations happening in the scope of the lifetime of a individual organism, I'm not interested in whether the mutations persisted under NS are equally distributed over the genome.

$\endgroup$
1
$\begingroup$

Well, for start, there are "mutational hot spots", regions that are more prone to mutation than others.

As for immune system genes, first of all, lung cells and heart cells and retina cells don't need to mutate those genes, because they don't use them.

But you are right that in immune cells there is a lot of DNA futzing in the sequences for the heavy and light chains, in order to generate diversity in T and B-cell receptors. Those receptor sequences are built in a mix-and match fashion, like building an outfit from a closet with a few pairs of pants and a few shirts. Add in some messiness in cutting out the specific sequences, and you have a fair bit of diversity in receptor sequences possible from a single genome.

Later, once a B-cell or T-cell meets a matching antigen, the cell multiplies, and each descendant cell is subject to somatic hypermutation, in the hopes that one of the tweaked sequences will better match the antigen.

But none of that is going to be very evolutionary relevant, since only mutations in gametes or gamete stem cells are passed on to the next generation.

| improve this answer | |
$\endgroup$
  • $\begingroup$ Ah, interesting. However, the immune system was only as an hypothetical example, are there any "mutational hot spots" that are evolutionary relevant? $\endgroup$ – Alex Sep 9 '14 at 3:00
1
$\begingroup$

If by "consistent" you mean homogenous, the answer is no. Regions conserved among individuals (and/or species) tend to accumulate less mutations (specially avoiding deleterious mutations). Even within a gene sequence, there are conserved regions which accumulate low number of changes, whereas non-conserved regions accumulate many mutations.

| improve this answer | |
$\endgroup$
  • 2
    $\begingroup$ It would be great if you could provide references for your response! $\endgroup$ – Behzad Rowshanravan Sep 9 '14 at 13:19
  • $\begingroup$ I'm a little confused, what do you mean by "conserved regions"? Are you referring to the survival of the mutations in coming generations due to NS? In that case, this is not what I'm searching for in my question, where I do not care about survival of the mutations happening. $\endgroup$ – Alex Sep 9 '14 at 13:35
  • $\begingroup$ @Alex, yes, by "conserved regions" I mean a fragment of the DNA or protein sequence that is conserved. That is, if you compare the same fragment among different individuals in the same species (or among different species) you will see that most of the nucleotides/aminoacids are either identical, or very similar (i.e. similar chemical or physical properties, e.g. same charge or size). These regions frequently are functional (e.g. a conserved protein region is involved in the catalytic activity) and mutations tend to be deleterious, hence they are eliminated by natural selection. $\endgroup$ – ddiez Sep 10 '14 at 13:22
  • $\begingroup$ @Bez, thanks, I will try to include some references, I am trying to find which ones are more appropriate so it may take some time. $\endgroup$ – ddiez Sep 10 '14 at 13:23
  • $\begingroup$ @Alex, if I understand correctly then, you want to know the mutation rate during the lifespan of an individual, and whether this is homogenous thorough the genome? That is challenging since there is no studies (AFAIK) on the evolution of an individual's genome over time. However, swbarnes2's comment about mutation hot spots may be indeed relevant to this. For example, this paper PMID:8832894 describes the existence of nonrandom patterns (mutation hot spots) in the gene TP53 (P53) associated with lung cancer. $\endgroup$ – ddiez Sep 10 '14 at 13:38

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.