Posted on 07/04/2006 8:42:50 AM PDT by DouglasKC
Reminder to self to respond later--must run for now!
Actually when they did the human genome project they ended up turning up way more differences than they expected. We already knew that there are a wide variety of single-base variants. But when they started doing the sequencing they also found that many people have differences in the numbers of copies of genes, and that some people also have portions of chromosomes reversed.
Single-base substitutions tend to be more common in noncoding DNA than in coding DNA because the DNA is less frequently scanned for repair and mutations are less likely to be eliminated as detrimental by natural selection. It's hard to say with these other differences. Some of them were found in multiple people, but the question there is whether they arose multiple times or whether those people share ancestry. Probably there are cases of both.
Nature had an article about this. "Human Genome: Patchwork People." Check, E. Nature. 2005, 437, 1084-1086.
Genome researchers now have a catch-all phrase for the vast array of rearrangements — including copy-number polymorphisms, inversions, deletions and duplications — that occur normally in the human genome. They call it structural variation, and have described at least 800 individual variants that, in total, account for about 3.5% of the human genome. And the sheer number of variants seems likely to catch up with the number of known single nucleotide polymorphisms — the single-letter 'typos' in the Book of Life. That makes structural variation a potentially major source of diversity. It is even possible that we're not all 99.9% similar, as the Human Genome Project predicted.. . .
Eichler has found that copy-number variants often occur in larger blocks of repetitive DNA called segmental duplications8. These blocks take up about 5% of the human genome, and occur in the same places in all of our genomes. They also seem to cause trouble. Scientists believe segmental duplications make it difficult for our genome to replicate itself faithfully during the processes that create eggs and sperm. Mistakes result in DNA rearrangements, such as deletions and inversions, meaning that new structural variants are created and passed down the generations.
Icelandic scientists reported earlier this year, for instance, that 20% of Europeans carry a large genetic inversion that is spreading throughout the population9. Women who carry the inversion have more children than those who don't — a classic sign that it confers some sort of selective advantage.
And studies comparing us with our chimp cousins have already linked structural variation to our divergence from the apes. Last year, scientists from the University of Colorado in Denver and Stanford University found 1,005 genes that differed in copy number among humans and four other primates10. This month, Eichler's group reported 651 likely structural rearrangements between chimps and humans11. The group counted 245 genes contained in these variants, including some genes involved in reproduction and drug metabolism. Eichler's group has also found that segmental duplications have created much more of our genomic differences from chimps than single base-pair differences7. There are 177 genes contained within the human-specific duplications. As such duplications are hotspots for evolution, those 177 genes could be partly responsible for creating the traits that make us human.
Agree 100%. We shouldn't atempt to micro-manage God. Might be some unintended consequences, huh? (Karma evolves from such actions???)
That is incorrect. Disproving that something couldn't happen a certain way is not the same as proving that something did happen a certain way. In this case, the assertion is that small changes cannot explain the archerfish. Such claims have been made by ID proponents numerous times before, about a variety of phenomena. One's inability to imagine (or accept) a series of causative events does not prove the impossibility of said events.
"teacup poodle and wolf"
Err, umm, the teacup is different than the poodle and the wolf? lol
"What with the human genome project, it'd be interesting to do longitudinal studies (if not in humans, then in other species) to map out the approximate number and distribution of the mutations.
Looks like you have the beginnings of a proposal for a grant.
I haven't heard of such but I will put the question to a group that should know.
"a) Is it true that the original single-codon mistranscriptions, etc., are 'uniformly distributed' within the germ cells, or are they "already" clustered in areas in which a screw-up would be minor instead of fatal? (thinking of your line later in the post "haven't touched on"...) This needn't posit intelligent design, just that the error checking mechanisms within DNA replication work a little harder on some regions than on others...
I don't have the information necessary to answer this question so I've passed it on to number of friends who can help.
Because of the 'gene proofreader' it would be difficult to tell. By the time we get the genome 'read' the built-in gene 'proofreader' would have beaten us to it.
"b) How many of the mutations are in the 'junk DNA'?
That question is difficult to answer because even though we can conclude that highly conserved non-coding regions are or may have been expressible, there may be parts of the non-conserved non-coding regions that do more than just look pretty.
I have forwarded this question to those with more information.
"c) You know, this experiment would be even more compelling in a reproduction of that experiment with the microorganism in the tank whose temperature was raised systematically. When the experiment was repeated, the same mutations came up. Right Wing Professor correctly pointed out that this was due to "saturation" of the genome--there were enough daughter cells created that every point mutation *was* exercised. What would be interesting would be to look at the distribution of *all* the mutations in the presence and the absence of the heating, and see if the distribution of the mutations differed. This is not an exact analogy since the unicellular critters in this experiment reproduced by fission, without gametes...but still kinda cool.
There may also be limits to the direction mutations can take given a specific starting point. In the 'fitness landscape' not all directions are equally 'bridgeable' the effect being that mutations cluster around a given fitness path.
"Another interesting point is that a mutation need not confer survival advantage, but survival advantage during breeding years, when genes will be passed on. But carrying this further, since propagation is all that matters, this would imply that marginal changes in attractiveness or being chosen as a mate would also be selected for rather quickly. But that begs the question, what is so "hot" about a brightly colored baboon's ass or a peacock's tail anyway? Why were THOSE particular hues the ones which (socially?) were chosen as desirable?
There are some studies that indicate the desire and the feature tend to 'evolve' together. This means that our 'choice' of partner, our concept of attractiveness, is in part genetic and in part a result of social convention. Once the evolution of sexual selection starts it would take as much energy to stop as to continue until the physical limits are reached. The peacock is a good example of this.
Some functions, whether selected through sexual preference or some other selection path, confer advantage beyond the reproduction years. If the function/feature of a parent/grandparent contributes to the success of the offspring, therebye affecting the number that reach their own reproductive age, it can be selected.
This means that being a good parent or a good grandparent can be part of the selection criteria. This is most useful to those organisms who have few children (which may in turn be the result of good parenting skills) Most selection is just part of the rather complex feedback system between an organism and its environment.
When evos speak about environment they are generally talking about the physical environment (weather, food, water, landscape) but more importantly about the other living organisms within the same ecological niche, including members of their own species. A change in predator or prey can do more to change the selection criterion than a change in landscape.
Its nice to see a good, serious science discussion on FR; its becoming all too rare to see that here nowadays.
Sure beats the flame wars, doesn't it? :-)
Cheers!
I think you'll find that if any genetic marker is not shared by the poodle and the wolf, then it will also be not shared by the teacup. Genetic markers common to the poodle and wolf may be shared by the teacup if it hasn't been washed recently.
"Its nice to see a good, serious science discussion on FR; its becoming all too rare to see that here nowadays.
I have to agree there.
GW is forcing me to think about questions I haven't contemplated for awhile and asking some new new ones to boot. He's got me scouring my list of links, written documents and even a few texts.
I'm deeply flattered by your implied compliment that my questions were worthwhile :-)
Cheers!
What's your relativistic inertial reference frame? At the beginning instant of the Big Bang, a perpetual calendar travelling at 99.99999999999% of the speed of light would mark out 6,000 years while 13.4 billion years elapsed here on Earth.
Why are you asking me questions? All your answers are in the bible.
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