In various wild species of Drosophila (fruit flies), there are a substantial number of stable inversion polymorphisms. Most of these are paracentric (not containing the centromere) inversions. Because of some peculiarities in Drosophila biology, crossovers within the inversion region do not make it into mature eggs and are not produced in males. Thus, there is no reproductive cost of being heterozygous for the inversions.

A consequence of all of this is that alleles of genes within these inversions behave as if they are completely tied to each other. These inversions easily encompass 300 or more genes.

That the inversions are stable in the population would seem to indicate either heterozygous advantage or perhaps different environments in which each prospers.

This is an extreme version of the situation David posits.

one thing, i believe lit. surveys show that non-sexish behavior crops up in 'complex' organisms now and then, but almost all these tend to be young lineages (bdelloid rotifers are the major exception). the implication is that they don't last over the long haul.

The beauty of chromosomes is that they enable one organism to have a whole spectrum of gene-gene relationships, from totally sexual to (almost) totally asexual. And this can change over long time periods.

I suspect that models assume that we have sex terribly infrequently, given how much sexual energy many of us put into thinking about their sex lives instead.

"It's certainly possible to have a lot more chromosomes than we have."

What does this mean ? How could we have more chromosomes than we have ? Or is this just a little word salad ?

Here:
http://www.pnas.org/cgi/content/...act/100/14/ 8319

Hello. I just found your site and I am curious about the research side of this science... what kind of things/variables that could occur in an animal Facility/research facility might affect 'gene expression' in the research animal that could cause an affect in the end result? This is a question I pose to those of you who are researchers. Does temperature and humidity variations and/or long term/short term exposure to cleaning chemicals cause an adverse effect?

Has anyone looked into this?

Can anyone direct me to where I might find the answers?

Reason for asking... Background: I am just barely allergic to wheat and chicken and do not appear to be reactive. I started having seizures at work for no apparent reason. They sent me to a specialist where I was placed in a study where I had electrodes placed on my head for 48hrs. Even though I told them not to give me anything to eat that was either chicken and/or wheat... they didn't listen. I was hungry so I ate the meal anyway. I normally do not react outwardly. I was overblown when I realized that I reacting at a cellular level... meaning that my brain waves were kicking only when I was consuming the wheat and/or chicken and not the other foods at that meal. And yet, I was not having a noticable reaction... it made me wonder.

It made me wonder what else can affect these research animals that yoou use to pull the gene expressions from.

Dee

David, I think you have a serious misconception about this. I posted a long comment about it on the copy of this post you put on your own site.

The bottom line: genes on the same chromosome which are not physically near one another (say, at opposite ends) have no more than a 50:50 chance of being inherited together.

Steven, Thanks for pointing that out. Although it would mean that the specific number of chromosomes not very important (though if 50:50 is correct it would still have a noticeable statistical impact), it doesn't invalidate anything else I said. Specifically, that arranging genes in chromosomes results in a spectrum of gene-gene relationships from totally sexual to almost totally asexual (for really close genes). And it doesn't invalidate any of my predictions (some of which have been confirmed by commenters).