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Chromosome Fusion

  1. May 8, 2009 #1
    I need someone who has been keeping an eye on the biological literature.

    It is by now an established fact that the human chromosome 2 originated as a fusion of two chimpanzee chromosomes (and I'm not about to dispute that, this post is in no way an advocacy of intelligent design :))

    There are other species in nature who's number of chromosomes differ by two, suggesting that fusion (or splitting) of chromosomes is quite common event. However, it is a quite drastic change of the genome and it is well-known that species with different chromosome number have great difficulty in reproducing, and always produces infertile offspring. In light of this, the chromosome fusion is a bit bizare; It cannot happen gradually (two chromosomes are either fused or they are not) and unless the exact same fusion happens to occur in a whole number of individuals of the population at the same time, it could not spread because of the infertility of the offspring. At least in the laymans world.

    Which brings me to my question: Has a mechanism for 1) how/why such chromosome fusions/splittings occur and 2) how such a fusion/splitting spreads in a population, been proposed?
  2. jcsd
  3. May 17, 2009 #2


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    Before getting to your question, can you provide a reference that supports this "established fact?" This is new to me.
  4. May 17, 2009 #3
    How about http://en.wikipedia.org/wiki/Chromosome_2_(human)" [Broken]'s references?
    Last edited by a moderator: May 4, 2017
  5. May 18, 2009 #4

    Negative, that is incorrect.

    Two chromosomes fused in the human genome during its genetic evolution, that is detectable by comparing a human chromosome map and a chimpanzee chromosome map, however none of the human genome originated from a chimpanzee, but rather from a common primate ancestor that did not have a fused chromosome.
  6. May 18, 2009 #5


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    Did you follow their references? They just go to other websites, but not research articles. :rolleyes: But, at least one of those sites cites an article in PNAS, which is getting a bit closer to a credible source.

    It seems Orion has an explanation that makes more sense.
    Last edited by a moderator: May 4, 2017
  7. May 18, 2009 #6

    A quick search in PubMed gives a number of references to the fact of chromosome 2 fusion early in human evolution. It seems as if this has been fairly well known about since the early 1990's.

    I take exception to the OP's statement that "it is well-known that species with different chromosome number have great difficulty in reproducing, and always produces infertile offspring.". "Always" is a poor choice of words here and would seem to be outright incorrect by the simple fact that our human ancestors did have such an event and were able to produce viable offspring....as well as many other species that have had similar events.

    However, if he is trying to make the assertion that this somehow "disproves" evolution, then I will just have to sit back and chuckle. :smile:
  8. May 20, 2009 #7
    The reference you are looking for is: http://www.nature.com/nature/journal/v434/n7034/full/nature03466.html
    Notice the precision of the identification of the fusion site (within 15 bases).

    This fusion event plays a large roll in the defense of evolution by pro-science cell biologist Ken Miller, who has used it as evidence in his recent book "Only a Theory: Evolution and the Battle for America's Soul".

    There is an excellent Youtube video of a lecture by Miller about this. Here is a small clip from it.

    Last edited by a moderator: Sep 25, 2014
  9. Sep 20, 2009 #8

    I have addressed this topic in a series of four essays on the blog "The Panda's Thumb". The last essay is here, and contains links to the previous three:


    Dave Wisker
  10. Sep 28, 2009 #9
    I'd like to add to this topic.:biggrin:

    I'll have to continue later and add a touch more. (I have to go digging for my old notes.:tongue2:) Also, after reviewing #3 under "References" in Wikipedia, it appears to me to be correct. :smile:
    Last edited by a moderator: May 4, 2017
  11. Oct 21, 2009 #10
    Thank you *very* much for your reply - although you didn't quite grasp the question which I was asking or the premesies under which I asked it:

    I think an unconditional apology for hinting that I'm "trying to make the assertion that this somehow "disproves" evolution" is very much in order :) I was as a matter of fact merely trying to enlighten myself as this issue pussled me.

    Now, I happened to discuss this matter with a biologist friend of mine some time after I made this post, and he pointed my errenous position out to me and explained that different cromosome numbers doesn't always mean that the offspring is infertile; such infertility more often originates from the subsequent diverging of the lineages.
  12. Nov 13, 2009 #11

    This is only a general theoretical estimation. My essays describe the unique circumstances in mammals and the human lineage that show that the decrease in fertilty for the end-to-end fusion that resulted in human chromsome 2 was probably 10% or less.

    Dave Wisker
  13. Nov 15, 2009 #12


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    D. Wisker, instead of referring to your blog, could you please point to the scientific reference that backs up your statements?
  14. Nov 21, 2009 #13
    Monique, the blog entries themselves are fully referenced, so I'm not sure what your point is. Simply reading the blog (rather than having me reproduce the argument again here) makes more sense to me. But a list of the references used in the argument follows:

    For a discussion of the dicentric issue:

    Sullivan BA, DJ Wolff, and S Schwartz (1994). Analysis of centromeric activity in Robertsonian translocations: implications for a functional acrocentric hierarchy. Chromosoma 103(7):459-67

    For the discussion of the fusion and its effect on fertility:

    Bardhan A and T Sharma (2000). Meiosis and speciation: a study in a speciating Mus terricolor complex. J. Genet. 79: 105-111

    Coyne, JA and HA Orr (1998).The evolutionary genetics of speciation. Phil. Trans. R. Soc. Lond. B 353: 287-305

    da Mota LSLS and RAB da Silva (1998). Centric fusion in goats (Capra hircus): Identification of a 6/15 translocation by high resolution chromosome banding . Genet. Mol. Biol. 21(1): S1415-47571998000100012(online publication)

    Nachman MW and P Myers (1989). Exceptional chromosomal mutations in a rodent population are not strongly underdominant. PNAS 86: 6666-6670

    Spirito, F (1998). The role of chromosomal change in speciation. In Endless Forms: Species and Speciation, DJ Howard and SH Berlocher, eds. Oxford University Press.

    For the probability of fixation within a deme (and evidence for meiotic drive in human fusion heterozygotes):

    Bengtsson BO (1980). Rates of karyotypic evolution in placental mammals. Hereditas 92: 37-47.

    Bengtsson BO and WF Bodmer (1976). The fitness of human translocation carriers. Ann. Hum. Genet London 40: 253-257.

    Hedrick P (1981). The establishment of chromosomal variants. Evolution 35(2): 322-332.

    Lande, R (1979). Effective deme sizes during long term evolution estimated from rates of chromosomal rearrangement. Evolution 33(1):234-251.

    Pardo-Manuel de Villena F and C Sapienza (2001). Transmission ratio distortion in offspring of heterozygous female carriers of Robertsonian translocations. Hum. Genet. 108: 31-36.

    Beyond the deme:

    Fix AG (1978). The role of kin-structured migration in genetic microdifferentiation. Ann. Hum. Genet. Lond. 41: 329-339.

    Hedrick PW & DA Levin (1984). Kin-founding and the fixation of chromosomal variants. Amer. Nat. 124(6): 789-787
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