Re: [Gecko] EVER HEARD OF?

[Greg Watkins-Colwell]

Title: Re: [Gecko] EVER HEARD OF?

on 12/30/00 7:47 PM, Michael Kearney at [EMAIL PROTECTED] wrote:

>The mechanism of parthenogenesis in whip-tailed lizards is such that the only source of genetic variation is spontaneous mutation

Is their mechanism the "auto-fertilization" type?  I can't remember.

Do they not have cross-over events during Prophase I?  What about independent assortment of homologous chromosomes (non-sister chromatid pairs) during Anaphase I?  Given that most of the Cnemidophorus that are asexual are also triploid or tetraploid, could these two mechanism (crossing-over and independent assortment) not work with too many copies of the chromosome?  These are supposedly standard eukaryotic mechanisms that occur in anything that does Meiosis, including ferns, mildew, Chihuahuas and sea monkeys.  But for every rule, there are exceptions.  Maybe Cnemidophorus has a way to avoid doing this.  

Spontaneous mutation is an amazing thing.  And it can account for a great deal of variation.  The cells within your body are not all identical to each-other as it is, yet they all started from the same zygote.  The cells in identical twins also need not be identical, especially since they are in two different individuals, despite the commonality of origin.  Imagine that a mutation occurs during early cleavage of an each twin embryo.  All resulting cells would carry that new information and thus not be identical to what started (and thus the twins not identical to each-other).  The odds of each individual randomly mutating in the same exact way....

What if the mutation occurred during gamete production.  If that gamete were to become an embryo, it would not be genetically identical to the parent, or to any sibling.

I may interpret the word "identical" more literally than others.  But even one base pair difference between individual cells means they are not identical.  If that mutation happens to be in the right place... and it affects gene expression, well things get even more exciting then.  And it's rather exciting to begin with!  ;-)


--
Gregory J. Watkins-Colwell
Dept. of Biology
Sacred Heart University
5151 Park Avenue
Fairfield, CT  06432

and

Yale Peabody Museum
Dept. of Vertebrate Zoology
170 Whitney Ave
PO Box 208118
New Haven, CT  06520-8118