Re: [asa] Theo-Neo-Darwnian Synthesis + Chromosome Fusion WAS Who do Adam & Eve represent? (Was: Was Adam a real person?

From: David Campbell <pleuronaia@gmail.com>
Date: Thu Apr 17 2008 - 13:59:09 EDT

A bit more on chromosome fusion:

The main problem arises when the offspring with 47 chromosomes tries
to produce gametes. Chromosomes pair up before meiosis, ensuring that
each gamete gets one of each chromosome. However, if the chromosome
pairs do not come out even, there's a significant risk of
misallocation. Thus, there would be selective pressure in favor of 46
chromosome individuals breeding with other 46 chromosome individuals
and 48 chromosome individuals breeding with 48 chromosome individuals.
 (Similar issues arise, e.g., in many polyploids. Much seedless fruit
is triploid-sorting out three matching chromosomes in meiosis doesn't
work well unless you're a freshwater Asian clam. Wheat is a
hexaploid, and the gene that keeps the three sets pairing up properly
has been identified. Delete it and the wheat doesn't do well with
seed production.)

Small, isolated populations are generally good for generating new
species because changes can spread quickly. Not only would that be a
good setting for a novel chromosome arrangement to have a chance at
establishing itself, but also it would be a good setting for
innovations distinguishing the human versus chimp lineages to become
established. A class in grad school, ca. 12 years ago, mentioned
studies on Italian mouse populations in isolated valleys that had
significant chromosome fusions, but I don't have more details. (Yes,
I know, details were attached to the back ends of de mice, but that's
not the information needed here.)

-- 
Dr. David Campbell
425 Scientific Collections
University of Alabama
"I think of my happy condition, surrounded by acres of clams"
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Received on Thu Apr 17 14:00:23 2008

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