Covenant Gardens, London
2007
I guess I will never really understand genetics. I know that we inherit a single copy of each of our 23
chromosomes from each parent. Later the
genes on these chromosomes are “expressed” as proteins, which inscrutably complicated and grotesquely misshapen blobs of amino acids go around
doing everything important in the body. I
don’t really understand how the body decides which gene from which chromosome(which "allele", I should say)
to use. In some cases the gene on one of
the aleles is completely “dominant” over the other – it, and only it, gets
expressed. But there are things like
shared dominance, co-dominance, etc.,etc. What’s a
geologist to do? In my field quartz always
is harder than feldspar, gravity always acts straight down, hot things always
cool off eventually. That’s the way the universe
ought to work- simple, invariant laws that, once understood, can be put to
work. Not so in genetics, apparently. Who designed this Rube Goldberg thing,
anyway?
I write this because I just read an article in the NY Times
telling of how female cells will methodically stifle one of their two X chromosomes. You know X chromosomes: get two of them, you’re
female, get an X and a Y, you’re male.
It appears that females somehow de-activate one entire X chromosome, by
attaching some protein called Xist to it.
If the article is to be trusted, one cell can deactivate the X it got
from Mom, while its neighbor deactivates the one from Paw. Why?
You get one copy of, say, chromosome 20 from each parent, but neither is
shut down completely. Why only X?
Maybe they will figure it out and explain it to me.
This sort of thing has relevance to cancer. If I understand, failure to deactivate one or
the other copy of X results in a superabundance of stuff, some of which causes
cell proliferation – e.g., cancer.
As Forest Gump would say, that’s all I have to say about
that. Read it yourself at:
Yes, the way I always understood it was that there are so many genes on the X chromosome, that if women had twice as many as men it would cause lots of problems. The inactivation of the 2nd X is to "even out" the score between men and women. Men have extra genes that women don't have on the Y, obviously, but not much. I think you have genetics down better than you think. I never heard of Xist. When I learned this stuff they didn't know how it happened. Cool.
ReplyDeleteI wish you had been able to work in this field. I think you would have gone very far. Dad
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