The mutations that have resulted in the genomes (and therefore the genes) of today's creatures are the result of:
1) point mutations. These affect only a single base pair of genetic sequence.
Point mutants and even sequence changes affecting only small regions are among the simplest changes to the genome sequence.
2) Break point mutations are the result of breaks in the chromosome and the resulting changes in the sequence. These are the result of a break in the DNA molecule that is making up a chromosome. These kinds of mutation can affect large areas depending the number of breaks on how DNA repair mechanisms owrk things out, like arms of chromosomes or only relatively small regions (like deleting a few base pairs), Simple results could be the removal, inversion (flip end-to-end), removal to a different location, duplications of regions, things like that. These kinds of changes can also affect individual genes (kind of small to intermediate sequence size) and can result in switching in and out whole sections of sequence and result in more complex genetic changes. This can take a part of one gene and stick it onto or switch it in or out of a gene's sequence. This can result in large and interesting changes in a gene's sequence or duplicating whole genes or gene regions. Duplicated genes can then be changed independently by point mutations so that one gene maintains the ancestral function while a second copy can be evolved to a new function.
Because these kinds of changes affect lots of genetic parts, they can have big effects on function. However, big changes are less likely to produce something that can survive (most would be lethal mutations).
3) There are also gene changes of genetic origin. These could include genome changes due to genetic transposons, retroviruses, and other things that move around or make duplications in the genome over generations of time. They produce similar genetic results to breakpoint mutations in that they move around chunks of sequence (either their own or some they might have picked up from their current or a former host). They can make thousands of copies of themselves in the genome, some of which might affect protein evolution.
Evolution sorts through thousands or millions of all these kinds of mutations to come up with a few useful changes that are adaptive.
These kinds of changes can account for a lot of current gene diversity.
There are at least most of the kinds of mutations that would be involved in generation current protein sequence. Which ever came last would be what you want I guess. I would also guess that those would be most likely to be point mutants, but probably not always.
KenJackson said:
Whether it's done or not is irrelevant. It's in use and extremely valuable as it is. And surely it's been valuable for a long time. So the last component must have been added to it to make it useful much more than a thousand years ago.
Hemoglobin is under different selection pressures depending on the environment it is found in. If a reproductive unit moves from an environment favoring one functional trait to another favoring a different traits (which can happen sometimes when people move) then the gene will experience new selective pressures and its sequence should change over a time of generations.
The evolution of a gene is frequently thought of as how the population of the genes sequences in the breeding population of the species changes over time. This will be on a generation time scale with a lot of sequence variants co-existing in a population.
