Talk:Chromosome 2

message: If you are familiar with the chromosome fusion event, please explain how it was possible for the first individual with a fused chromosome 2 to find a mate with a similarly fused chromosome 2.
The following explanations come to mind:
1.  Perhaps one individual ape had a random, dominant mutation that caused all or most of his/her descendants to have chromosome 2 fusions.  Inbreeding between those descendants resulted in a new species (humans) that could not breed with non-humans.
2.  Perhaps a random, dominant mutation temporarily suppressed the genetic mechanism that causes fetal death when mismatched chromosomes are detected, so that individuals with fused chromosome 2 (i.e. humans) were able to successfully breed with non-humans who did not have fused chromosome 2, and some of the resulting descendants retained that mutation for a few generations.  But eventually the mutation was lost and thereafter no humans retained the mutation that made human/ape mating possible.
3.  Perhaps there was a dominant pre-fusion mutation in one ape that was copied into all descendants, all of which had unfused 2a and 2b chromosomes and this permitted sucessful mating with non-mutated apes.  Perhaps fusion resulted if both male and female carried the pre-fusion mutation but no fusion if only one carried it.  And perhaps those with fusion could successfully mate with non-fused apes that had the pre-fusion mutation and produce babies with fusion.
Reliable references for such explanation(s) are needed.  Greensburger (talk) 06:09, 9 May 2010 (UTC)
replies: text: I can't claim to be "familiar with the . . . event" even on a theoretical basis, but from my lay standpoint I can't see any particular problem. In the first individual(s) with the fusion, the two separate chromosomes from an unmutated mate would presumably still have been able to align with the end-fused version without (much) difficulty, and there would have been little or no discernable effect. As the fused version proliferated in the population, some fused-fused pairings would also have occurred with increasing frequency. Over (long) time, reductions of the fused telomeres and doubtless other changes would have made successful fused-unfused pairings increasingly less likely to be successful, and gradually two "cryptic-species" (see Cryptic species complex) would have developed, though for a very long time they would not have appeared phenotypically different. Speciation is, I think, rarely a single generational event; more often it will take hundresds to thousands of generations. 87.81.230.195 (talk) 17:01, 13 May 2010 (UTC)
replies: text: Perhaps only a dozen or so generations were sufficient to produce thousands of apes with the pre-fusion mutation.  If inbreeding between apes with the pre-fusion mutation resulted in fusion, speciation could result in only one generation, consisting of hundreds of babies that had the fusion.  If the fusion conferred only one significant survival advantage (for example patches of bare skin that produced more vitamin D), most of the next generation could be fused because they were healthier and produced more healthy babies. Greensburger (talk) 02:51, 14 May 2010 (UTC)
replies: text: Perhaps, but also perhaps not, depending on how large (and dense) the population was (aside from any actual genetic viability problems). I believe current thinking is that the absolute numbers of our ancestral species (plural) were quite low and also that they (due to their ecological niches) may have been quite thinly dispersed, so proliferation of the fused genes might also have been slow. We also don't (so far as I know) have a good idea of how long it would have taken for fused-unfused interfertility to develop, nor do we know if either of your "ifs" were actually the case. At this stage of our knowledge much about our speciation is still speculation. I too would welcome guidance to further references on these questions, if any exist. 87.81.230.195 (talk) 16:46, 14 May 2010 (UTC)
thread_title:  Post-Fusion evolution 

message: At the end, the article suggests that a fusion event such as an 8/9 fusion could be disseminated across an existing population.
I find it very unlikely that post-fusion there would be significant mixing of the now genetically distinct populations.
Consider the Equine Species.  Each member of the equine species has a different number of chromosomes.  
:Horses have 64 Chromosomes.
:Donkeys have 62 Chromosomes.
:Zebras have 32 or 46 Chromosomes.
When a horse and donkey crosses one gets a mule with 63 chromosomes.  The first generation crossbred has a complete set of genes and is viable.  However, the odd number of genes, as well as improperly matched gene pairs disrupts meiosis, and second generation offspring does not receive the full gene compliment and is not viable.  Or, perhaps only a small fraction of the second generation offspring would receive the full genetic compliment to be viable leading to the novel major mutation to eventually die out.  This helps ensure a stable gene compliment across a population.
The gene fusion likely occurred in a single family, possibly with a rapid succession of evolutionary changes.  The new fused population then spread out in parallel with the existing hominid population.  But rather than merging with the existing population, the chromosome fusion population developed independently, and eventually out competed and replaced the existing population.Keelec (talk) 19:36, 9 November 2010 (UTC)
thread_title:  Disseminating "Fusion" across an existing population 

message: What's the point of the "Genes" section of the article?  It seems to be just a random selection out of many.  I don't detect any criteria.  I presume these are not the Chr. 2 genes of "major importance" (by whatever definition). -R. S. Shaw (talk) 23:11, 30 June 2011 (UTC)
replies: text: I'm sure many people can use it for some reason or another, even if it's not complete or a list of genes of major importance. Of course, the list can always be expanded or made more relevant. Besides, don't you think it's a tiny bit important to mention what genes are in the chromosome? It seems kind of silly to talk about a chromosome (whose sole purpose in existing is to carry genes!) without mentioning the genes it carries. --TAW (talk) 00:31, 1 July 2011 (UTC)
thread_title:  "Genes" section 

message: Do we know if Neanderthals had a fused chromosome 2. Did it happen before the last common ansestor of Humans and neanderthals branched off  — Preceding unsigned comment added by Jimmy saville (talk • contribs) 13:36, 4 February 2012 (UTC)
replies: text: According to the article, A High-Coverage Genome Sequence from an Archaic Denisovan Individual Matthias Meyer Et Al, linked as the third footnote, Denisovans carried the 2A/2B fusion.  From the data, the authors concluded that the Neanderthals also likely carried the mutation, and that it had occurred somewhat earlier in human evolution, although they did not present Neanderthal specific data.Keelec (talk) 21:08, 6 February 2014 (UTC)
thread_title: Neanderthals

message: An ip anon inserted his or her creationist propaganda here a week ago, and all the edits since have been trying to clear it up. The article clearly requiresw more eyes as this isnt the first time. Well done for people trying to report and fix the issue. ♫ SqueakBox talk contribs 01:19, 3 September 2015 (UTC)
thread_title: Creationist propaganda

message: The first sentence of the Evolution section says All members of Hominidae except humans, Neanderthals, and Denisovans have 24 pairs of chromosomes. This is misleading. Modern humans, Neanderthals, and Denisovans are the only members of Hominidae known to have 23 pairs of chromosomes. However, we don't know when the transition occurred. Although H.heidelbergensis 750,000 years ago seems likely, for all we know H. habilis or even Australopithecus could have had 23 pairs of chromosomes. Zyxwv99 (talk) 18:27, 2 August 2017 (UTC)
thread_title:  All members of Hominidae except humans, Neanderthals, and Denisovans 

message: The ncbi link includes all the pseudogene's as well as normal functioning genes. Should Pseudogenes be included in the Wikipedia list also? Opinions please Leveni (talk) 10:44, 8 January 2021 (UTC)
thread_title: Pseudogene