This is the second part of a repost due to mail failure. Please note
my change of address from sjones@iinet.net.au to sejones@ibm.net.
Sorry if this was received already!
On Mon, 24 Jun 1996 22:01:29 -0700, Lynn J. Fancher wrote:
[continued]
SJ>Indeed, Gould points out that though the differences between man
>and chimp at the genetic level might be minor, the *organisation* of
>that genetic material at the chromosome level is major:
>"The genetic differences between humans and chimps are minor,
>but they include at least ten large inversions and translocations.
>An inversion is, literally, the turning around of a chromosomal
>segment. (Gould S.J., "Ever Since Darwin", Penguin: London, 1977,
>p55)
>
>Since even one such chromosome inversions would probably confer
>sterility:
LF>snip of Gould quote
>
>Sorry, but this is another erronious claim, even if you make it appear
>that Gould is making the claim.
I don't make "make it appear". Gould *is* "making the claim"! Read
the chapter for yourself. Besides, he has made it elsewhere:
"Hybrids, with different forms and numbers of maternal and paternal
chromosomes, will usually be sterile because chromosomes have no
partners for pairing before meiosis-the "reduction division" that
produces sex cells with half the genetic information of body cells."
(Gould S.J., "The Ant and the Plant", "Bully for Brontosaurus",
Penguin: London, 1991, p484)
LF>As an undergraduate, I worked for quite a while in a Drosophila
>(fruit fly) lab. The director of the lab had spend years developing
>dozens of strains of Drosophila which were homozygous for a variety
>of different translocations. These flies were perfectly healthy,
>and it would have been impossible to create them if flies which were
>heterozygous for those translocations were unable to breed, since
>these homozygous strains were the offspring of just such flies.
>(The flies were used for an extensive study looking at the
>comparative damage due to small amounts of extra chromosome or small
>amounts of missing chromosome--by making crosses among the various
>different translocation strains.)
The operative clause is "The director of the lab had spend years
developing dozens of strains of Drosophila..."! This is an analogue
of the work of an Intelligent Designer, not of the Blind Watchmaker!
Besides, these fruit-flies were still fruit-flies. The particular
"translocations" in these fruit-flies may be different from those in
man.
LF>Also, geneticists are all familiar with a famous line of flies
>called "Muller 5" flies. These were engineered by H.J.Muller to
>carry so many inversions and translocations that they could not mate
>with normal flies unless absolutely no crossing over occured. But
>they could mate with each other just fine, thank you.
First, I note the analogue with Intelligent Design: "These were
engineered by H.J.Muller...".
Second, you confirm that "they could not mate with normal flies"
because of these "inversions and translocations".
Third, it is non-controversial that individuals with chromosomal
"inversions and translocations" can breed with each other. After
alll, Homo sapiens has these "ten large inversions and
translocations" and he can "mate...just fine" with other Homo
sapiens!
LF>Just in case you imagine that what works in fruit flies won't work
>in humans, you should be aware that the human species harbors a
>number of translocations. For example, a small percentage of people
>carry a translocation between the 21st and 15th human chromosomes.
>These people are perfectly normal, and they are fertile.
Actually, when it is carried, it is between the 21st and 14th
chromosome:
"Down syndrome is always due to an extra chromosome 21 but in about
5% of cases the extra chromosome is attached to another chromosome,
often chromosome 14. This abnormal chromosome arose because a
translocation occurred between chromosome 14 and 21 in one of the
parents, or even generations earlier. Therefore, when Down syndrome
is due to a translocation, it is not age related, and instead it
tends to "run in the family" of either the father or the mother."
(Mader S., "Biology", Wm. C. Brown: Indiana, Third Edition, 1990,
p206)
LF>The only way such a condition is detected is in the case where,
>in the production of a gamete, a normal 21st chromosome ends up in a
>gamete with a 15/21 translocation chromosome. If this then
>participates in fertilization with a normal gamete, the zygote will
>in effect have three 21st chromosomes, producing a condition known
>as "translocation Downs." A small but persistent percentage of
>Downs Syndrome cases are of this type. Offspring of the carrier of
>these translocated chromosomes often inherit the balanced set of
>translocated chromosomes--in other words, they will have one normal
>15, one normal 21, and one translocated 15/21. And they are
>perfectly normal. And fertile. Just as their translocation
>carrying parent was.
Down's Syndrome is not lethal because it affects the comparatively
minor No. 21:
"In humans, additions and deletions of chromosomes, particularly the
large chromosomes (groups A B, and C), almost always result in
lethals. Some newborns with extra chromosomes of the smaller groups
such as G (e.g., chromosome 21) survive but show multiple physical
and mental abnormalities...A small autosome, chromosome 21 (Fig.
19.3), added to the normal complement (47, +21) causes Down
syndrome." (Gardner E.J, et al, "Principles of Genetics", Wiley,
Eighth Edition, 1991, pp512,514)
Gould says that the chromosomal differences between humans and chimps
"include at least ten large inversions and translocations." (Gould
S.J., "Ever Since Darwin", Penguin: London, 1977, p55). Therefore
the comparison between Drosophila and Downs Syndrome is irrelevant.
LF>The message here is that translocations or inversions do not
>immediately mean sterility, even in the heterozygous condition. In
>fact, if the translocation is reciprocal, balanced and homozygous, all
>you've got is an invidual with unusual chromosomes. Problems can arise
>in translocation or inversion heterozygotes during meiosis if certain
>kinds of crossover events occur, but if none of those kinds occur, even
>though the pairing of the chromosomes may look funny, no problems
>arise.
See above.
SJ>one might ask how did this chain of alleged descent from
>chimp-human ancestor to human, manage to survive these major
>chromosomal dislocations, each of which would render the link
>sterile?
LF>Well, just in case you didn't get the point above, I'll directly
>answer this. Since merely having a translocation doesn't
>necessarily mean disaster, and a certain number of individuals in,
>say, the species _Homo_sapiens_ are known to carry translocations,
>etc., with no dire consequences, that pretty much answers your
>question.
No it doesn't. You have cited a couple of *minor* examples and hoped
that solves a *major* problem.
LF>Now all you have to do is invoke a bottlenecking event or
>two (common in this world of ecological upheavals) to get new
>chromosomal arrangements fixed in a new population, a bit of
>reproductive isolation, and two or three fixed translocations or
>inversions down the road, you _have_ accumulated enough
>rearrangement to make it impossible for the old and new chromosome
>sets to get along together during meiosis, and voila you have split
>one species into two.
"Voila" is indeed the word. That's what magicians say when they wish
to create an illusion, isn't it? :-) ReMine says:
"Yet evolutionary illusions are so thorough that evolutionists
themselves are unaware. So I refer to an imaginary evolutionary
theorist. The theorist is the magician who produces illusions in the
mind. The illusions are achieved by selectively invoking concepts,
ideas and arguments. The theorist invokes concepts A and B to
misdirect you and accomplish end C. The central illusion of evolution
lies in making a wide array of contradictory mechanisms look like a
seamless whole. There is no single evolutionary mechanism-there are
countless. Evolutionary theory is a smorgasbord: a vast buffet of
disjointed and conflicting mechanisms waiting to be chosen by the
theorist. For any given question, the theorist invokes only those
mechanisms that look most satisfying. Yet, the next question elicits
a different response, with other mechanisms invoked and
neglected." (ReMine W.J., "The Biotic Message: Evolution Versus
Message Theory", St. Paul Science: Saint Paul, 1993, p24)
LF>Incidentally, one of the points of that Drosophila study I
>mentioned was to establish (which it did without question) that the
>translocation or inversion itself creates no genetic problems for
>the organism.
It depends where they are.
LF>Now farewell. I am off to more rational hunting grounds. Sorry
>to ripple your pool.
In this "pool", it was a fairly minor "ripple"! Thanks for the
illustration of Darwinist wishful thinking! :-. Farewell.
Regards.
Steve
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