Chromosome 2 Fusion

I’m going to pull these chromosome 2 fusion comments into a new post. Interestingly, everyone acts as if this is new data. This has been known for decades, as long as karyotype analysis and chromosome banding studies have been around. The sequencing data has merely confirmed more dramatically the argument for a chromosome fusion.

17 comments to Chromosome 2 Fusion

  • Hi Randy- are you familiar with ISCID ( http://www.iscid.org ) . Is this a new ID-type of science group? Do you have any opinions on this movement/organization?

    …Bernie

  • Randy Isaac

    @Bernie Dehler
    I’m aware of it, though “familiar” is too strong. It’s about 8 to 10 years old, I think, and is an association of ID researchers that Dembski heads. I haven’t done any analysis of their work.
    Randy

  • Thanks Randy- I just looked it up on wikipedia too:
    http://en.wikipedia.org/wiki/ISCID

    It looks to be defunct:
    “As of September 2008 the society’s website stated that “ISCID is no longer being managed as an organization”.[10]. Its last “Society announcement” and last journal publication being in late 2005,[11] no updates on its essay contests and moderated chats since 2004,[12][13] and no conferences or workshops announced since 2003.[14][15]“

  • Randy Isaac

    Can anyone recommend some useful articles and/or books that discuss the chromosome fusion process? The whole issue of heterozygotic vs homozygotic processes and all the specific mutations and changes that need to happen have presumably been spelled out somewhere but I’m not sure where.

    Randy

  • Charles Austerberry

    Randy:
    One interesting recent paper about chromosome fusions reports work on grasses (such as wheat).
    http://www.pnas.org/content/106/37/15780.abstract
    Apparently chromosome fusions can happen in different ways, and which mechanism is most likely might depend upon the sort of organism.  In the grasses, insertion of one chromosome into another appears to have happened several times.  Whether via insertion of one into another as in grasses or via fusion of ends (fusion of telomeres) as in mammals, the main difficulty with fusion of entire chromosomes is that after the fusion event you’ve got a single chromosome with two centromeres (and thus, during mitosis and meiosis, there can be problems with chromosome segregation).  For that reason, people had speculated that in the grasses, the right and left arms of a chromosome might independently insert into two separate recipient chromosomes. The centromere that had been between those arms would fail to insert anywhere and be lost, thus avoiding the problem of adding a second centromere to an existing chromosome.  But, the data in the recent grass paper suggest that entire intact chromosomes have inserted into recipient chromosomes. Maybe inactivation of one of the two centromeres can happen rather quickly, perhaps first through epigenetic silencing, prior to more permanent inactivation via mutation.  Likewise, the telomeric fusion event that apparently led to human chromosome 2 might have been facilitated by quick epigenetic inactivation of one of the two centromeres.
    Telomeres (which are normally only at chromosome termini) winding up in the middle of a chromosome formed by fusion of two pre-existing chromosomes is likely not a big problem, at least not as big of a problem as having two centromeres.  As Carol Greider might have mentioned at the AAAS talk, the ciliated protists she studied have telomere-like sequences at several internal locations within their micronuclear chromosomes, as does human chromosome 2.  Now it is true that ciliated protists do strange things with their chromosomes when somatic macronuclei develop from germ-line micronuclei.  The micronuclear chromosomes get fragmented into a number of smaller macronuclear chromosomes, which then get telomeres added to their newly-created ends.  But the stable presence of telomere-like sequences in the middle of ciliate micronuclear chromosomes tells me that human chromosome 2 is not unique in having relics of ancient telomeres at internal (non-terminal) locations.
    Cheers!
    Chuck

  • Charles Austerberry

    One more reference on chromosome fusions:
    http://www.springerlink.com/content/186u771668271k1r/
    This one is useful because it focuses on primate chromosome evolution.
    Cheers!
    Chuck

  • Charles Austerberry

    Dr. Rana at Reasons to Believe has an article regarding the chromosome 2 fusion on page 6 of the current issue (Vol. 2, No. 3) of RTB’s e-zine.  The e-zine is a pdf file: http://www.reasons.org/files/ezine/ezine-2010-03.pdf.  Because of RTB’s a priori disbelief that humans could have evolved from other animals, the article employs tortured logic typical of RTB’s literature about biological evolution.  But in other ways, again typical of RTB, the article is refreshing and encouraging.  Unlike many other antievolution organizations that simply get the facts wrong  – rhetorically asking, for example, how any human ancestor could survive losing an entire chromosome’s genes, as if any biologist really thought that’s how chromosome number is reduced – in contrast RTB acknowledges and accurately describes chromosomes, telomeres, centromeres, and the fusion hypothesis. In fact, Dr. Rana suggests that God used existing chromosomes when fashioning human chromosome 2!  To me, it’s a rather small step from there to the theistic evolution/evolutionary creation perspective that I think best accounts for chromosome 2 and myriad additional data.
    Implying that creation and natural evolution are mutually exclusive alternatives, Rana suggests that a Creator was involved in fashioning human chromosome 2 because the odds of human chromosome 2 evolving are very low.
    If only RTB could see the Creator’s involvement through biological evolution as clearly as RTB sees the Creator’s involvement through cosmological evolution!  I remain hopeful that RTB’s relative honesty and openness towards data will gradually bring their biological science up to par with their astronomical science.
    Chuck Austerberry
     

 

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