At 12:56 PM 1/25/00 -0800, Bill Cole wrote:
>From: "Rebecca Allbritton" <[EMAIL PROTECTED]>
>|
>| Amazing. What Michelle wrote was pretty much what I was thinking, so
>I've
>| left it. =) I'd also add that since it is difficult to introduce strange
>
>I need more help to understand this. Please reduce my ignorance.
>
>Let's say that there IS a genetic propensity for kinked tails, that the
>kinks are not all due to baby accidents (and I can see where the accidents
>would produce a lot of kinks also).
>
>Rebecca says it's unwise to continue breeding from a gerbil with a kinked
>tail. Michelle agrees and likened that to breeding dogs and cats along
>lines that eventually display malformations, like hip dysplasia etc. (My
>favorite example is from long-ago Albert Payson Terhune books about
>collies, where he persistently ranted about collie breeding that had made
>their noses almost non-functional, but somehow more satisfying to human
>viewers.)
Slightly related anecdote: Collies are so dumb they will walk into walls.
Ask any collie breeder in the US about it. They get very embarassed.
Apparently they have trouble judging distances & will run into the corners
of things. It's not actually because they're as dumb as sight hounds (e.g.
Afgan hounds), but because their eyes are in the wrong place.
>How do we know that a kinked tail is related to anything that might be
>harmful to the animal? Do we just GUESS that the tail might be related to
>some harmful gene that will show up in later generations?
Because mammals are related to mammals. That's why people are bothering to
study, for example, spotting in mice: white spots (indicating lack of
melanophores) are linked to all sorts of neurological defects, because the
melanophores and nerve tissue both originate in the embryo from the same
area of the neural crest. White spotting in mice is linked to neurological
abnormalities that will show up in the homozygous state. However, it's not
to the point where you can look at a mouse with white spots and say, oh, it
has this defect and can't make the correct form of this particular protein.
It's to the point that in a particular strain of inbred mice, you can
say... wait, I'm digressing. =) We use animal models to study human
diseases & processes all the time.
We know rather than guess because kinked tails in mammals are caused (aside
from injury) by the same series of genetic defects. Like siamese & burmese
function the same way in all animals that have those alleles: it's on the
albino locus, and they get darker where they're colder (nose, ears, tail,
feet.)
In the single animal, this mutation may or may not be a problem, but down
the road in future generations, you can create problems that are more
severe than the one you started with if you combine an animal carrying but
not expressing that gene with another one carrying (and maybe not
expressing) that gene. So no, we're not guessing. The "messed up tail gene"
is itself the bad gene.
>I don't agree that "genetic purity" is something to be sought, for either
>animals or humans. I'm from a pretty limited WASP gene pool, but I don't
>think that's especially good for the future of my species.
One of the interesting things to me about genetics, is in animals you
always try to start out with the wild or non-mutant type. Nobody is willing
to step anywhere near that in humans, for fear of offending anyone. Maybe
some day in the future someone will be able to do it. I would be very much
suprised if dark black skin is not found to be the non-mutant type, because
lack of pigment in hairless or lightly haired skin is very non-adaptive,
and just asking for skin cancer. Melanin protects our skin from so many
different environmental assaults -- if you smoke, nicotine & other
carcenogens get trapped in your melanin. You even have to have melanin in
the cells in the structures of your ears, in order for them to be
functional. I have no interest in speculating on this on the list, as it's
way off topic, but it's something interesting to think about.
all the best,
Rebecca...
