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Member (Idle past 1405 days) Posts: 20714 From: the other end of the sidewalk Joined: |
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Author | Topic: "Macro" vs "Micro" genetic "kind" mechanism? | |||||||||||||||||||||||||||
Rrhain Member Posts: 6351 From: San Diego, CA, USA Joined: |
RAZD writes:
quote: To some degree, at least, yes. If you look at the human chromosome 2, it looks exactly like a fused chromosome 2p and 2q of chimps, gorillas, and orangutans. Chromosomes have telomeres on the end...long strings of code on the end that essentially let the enzymes know that the end of the chromosome is coming up. If you look at the human chromosome 2, there is a telomeric sequence right in the middle of one of the branches. If you look at the tagging sequence, the rest of the chromosome below the telomeric sequence is a reversed version of the other primates chromosomes: Human: centromere-abcdefg-telomeric-zyxwvut-telomere Chimp: centromere-abcdefg-telomerecentromere-tuvwxyz-telomere And while we're on it, there's the evidence of the centromere scar on the human chromosome 2. The full description: Human: telomere-123456-centromere-abcdefg-telomeric-zyxwvut-centromeric-0987-telomere Chimp: telomere-123456-centromere-abcdefg-telomeretelomere-7890-centromere-tuvwxyz-telomere It is quite clear that the human chromosome 2 is a fusion of ancestral chromosomes 2p and 2q:
Human Chromosome 2 is a fusion of two ancestral chromosomes Rrhain WWJD? JWRTFM!
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pink sasquatch Member (Idle past 6022 days) Posts: 1567 Joined: |
RAZD writes: can one develop a chromosome family tree? Yes. In fact, there is a group working on characterizing the "ancestral placental mammalian karyotype" - putatively the genome (at chromosomal segment level) of the mammalian species from which evolved all other mammals. A review on the project (a few years old):
Evolution of mammalian genome organization inferred from comparative gene mapping. Genome Biol. 2001;2(6):REVIEWS0005. Epub 2001 Jun 05.Murphy WJ, Stanyon R, O'Brien SJ. Laboratory of Genomic Diversity, National Cancer Institute, Frederick, MD 21702-1201, USA. Comparative genome analyses, including chromosome painting in over 40 diverse mammalian species, ordered gene maps from several representatives of different mammalian and vertebrate orders, and large-scale sequencing of the human and mouse genomes are beginning to provide insight into the rates and patterns of chromosomal evolution on a whole-genome scale, as well as into the forces that have sculpted the genomes of extant mammalian species.free pdf: NCBI Original research from the same group (more recent):
The origin of human chromosome 1 and its homologs in placental mammals. Genome Res. 2003 Aug;13(8):1880-8. Epub 2003 Jul 17.Murphy WJ, Fronicke L, O'Brien SJ, Stanyon R. Laboratory of Genomic Diversity, National Cancer Institute, Frederick, Maryland 21702, USA. Developing ordered gene maps from multiple mammalian species coupled with chromosome-painting data provide a powerful resource for resolving the evolutionary history of chromosomes and whole genomes. In this work, we recapitulate the evolutionary history of human chromosome 1 and its homologs in placental mammals, putatively the largest physical unit in the ancestral placental genome. Precise definition of translocation exchange breakpoints in human, carnivore, cetartiodactyl, and rodent-ordered gene maps demonstrate that chromosome breakpoints, previously considered as equivalent, actually represent distinct chromosome positions and exchange events... RAZD writes: can {seperation \ duplication-modification \ addition \ deletion} of chromosomes be used to track "macro" levels of evolution the way mutations within gene sequences is used? No, at a simple level, since separation/duplication/modification/addition/deletion of chromosomes is really separation/duplication/modification/addition/deletion of genes - the gene or regulation level changes effect evolution, whether micro- or macro-. Chromosome level changes do not, except when those changes result in alterations at the gene level. My personal bias is that structure of gene families and complexity of regulation will define macroevolution more than chromosome-level changes.
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NosyNed Member Posts: 8996 From: Canada Joined: |
A good question; my first thought: a possible mechanism would utilize a "kind"-specific subset of absolutely mutation-proof genes, perhaps involved in reproduction. These genes would represent the signature for each "kind" and thus define each kind.
I'm going to be very lazy and not look anything up. This is off the top of my head. The mutation-proof genes you want are there! As I recall there are certain processes involved with cell division that are very, very common (not exactly mutation proof but nearly). They are so crucial that if they mutate the result is selected out. So these define "kind" as you have suggested. However, it seems that all forms of life carry them. This message has been edited by NosyNed, 07-05-2004 08:16 PM
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RAZD Member (Idle past 1405 days) Posts: 20714 From: the other end of the sidewalk Joined: |
or do lumberjacks make up the chorus?
{"I'm a lumberjack and I'm okay ..."} what about computer generated? create a program to evolve new arguments ... ahahahahahahaaaaa we are limited in our ability to understand by our ability to understand RebelAAmerican.Zen[Deist
{{{Buddha walks off laughing with joy}}}
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pink sasquatch Member (Idle past 6022 days) Posts: 1567 Joined: |
One Million Dollars a Month. One Million Dollars a Month. I'm in, perhaps as a "reasonable professorial type" - we might need a few of those to lend legitimacy. Perhaps after a year or two, when we've filled our coffers beyond our wildest dreams, we can slowly start slipping pro-evolution/anti-creationist propaganda in to really confuse the rubes...
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RAZD Member (Idle past 1405 days) Posts: 20714 From: the other end of the sidewalk Joined: |
so that makes us all one kind?
don't think that helps the creationists ...
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RAZD Member (Idle past 1405 days) Posts: 20714 From: the other end of the sidewalk Joined: |
sweet. I knew there was a different number 42 (2x21) human and 46? (2x23) chimp?
also different number between horse and donkey is given as reason for the sterility of the mule.
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RAZD Member (Idle past 1405 days) Posts: 20714 From: the other end of the sidewalk Joined: |
thanks. do you know what current theories there are for changing numbers of chromosomes? one obvious one is polyploidy, but it seems a little bit like a sledge hammer when a jewelers tap is more appropriate.
we are limited in our ability to understand by our ability to understand RebelAAmerican.Zen[Deist
{{{Buddha walks off laughing with joy}}}
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RAZD Member (Idle past 1405 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Or use the profits to fund research? (oh the irony eh?)
Of course you could also become your own critic just to keep the flames going? we are limited in our ability to understand by our ability to understand RebelAAmerican.Zen[Deist
{{{Buddha walks off laughing with joy}}}
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pink sasquatch Member (Idle past 6022 days) Posts: 1567 Joined: |
Hey Nosy,
So these define "kind" as you have suggested. However, it seems that all forms of life carry them. What an idea you've tripped upon! If there is only a single "kind" that includes all life, then there is no need for this silly micro- and macro-evolution stuff, since evolution only occurs within "kind." But seriously, I think you're talking about certain basic gene domains that are translated into the individual activities of a protein - in many cases these are highly conserved (though I'm not sure if any are completely conserved, especially since neutral mutations would be allowed). These domains are important because they've allowed the evolution of countless genes with the same basic activity, but different overall activity due to differences in surrounding sequence or addition of other types of domains. Thus every single gene did not have to arise by chance, though the ancestral domain may have. In any case, these domains are short stretches of sequence - even highly conserved genes like those coding for the ribosomes are quite divergent in sequence, even if their activity domains are identical. I'd been interested to find out which gene holds the title for the most conserved sequence during evolution.
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Rrhain Member Posts: 6351 From: San Diego, CA, USA Joined: |
RAZD responds to me:
quote: Just because I'm being pedantic: You do know those numbers can't be right. If I fuse two chromosomes into one, I have only lost one chromosome, not two. Thus, if humans are n (diploid), then chimps must be n+2 (diploid) and not n+4. OK...enough being pissy. Humans have 46, our close primate relatives have 48.
quote: Yes, but that in and of itself is not sufficient. Przewalski's horse has 66 chromosomes compared to the common horse's 64. And yet, they can breed and produce fertile offspring...with 65 chromosomes. So yes, differing chromosomal count is a problem for producing fertile offspring, but it is not a "never" criterion. Rrhain WWJD? JWRTFM!
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pink sasquatch Member (Idle past 6022 days) Posts: 1567 Joined: |
do you know what current theories there are for changing numbers of chromosomes? Depending on how a chromosome splits, or two chromosome fuse, there isn't necessarily a major detriment to the function of any of the genes on those chromosomes. The real problem is during cell division - depending on where the centromeres end up, huge chunks of genetic info can be lost or gained during division. In some rare cases in mice fusions have spontaneously arisen that don't wreak havoc on chromosome sorting and reproduction - if you are interested you might do a search on "Robertsonian translocations," since I'm feeling a bit rusty on the subject. (A similar example in humans is the Philadelphia translocation, though it hybridizes two genes, resulting in childhood leukemia...) I would think that if you had a small subpopulation arise with a chromosome fusion or division that was reproductively incompatible with the parental karyotype, you could potentially end up with reproductive isolation and speciation. As far as how splits/fusions/rearrangments occur, I'm fuzzy on the details, though I know they are a very active area of study. I know there are "recombination hot-spots" on some chromosomes that facilitate recombination errors (they are often large areas of repetitive sequence that confuse the DNA handling proteins). Chromosome breakage can occur with certain environmental insults (caffeine, for one, which is bad for coffee addicts like myself...), though they may have to occur after a fusion event so that following the break both pieces have a centromere to avoid loss during division.
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coffee_addict Member (Idle past 477 days) Posts: 3645 From: Indianapolis, IN Joined: |
RAZD writes:
Here is one obvious one, but not so obvious for most people. The Y-chromosome is getting smaller my the generation. Many biologists think that it's going to disappear or join the X-chromosome in the distant future. Wouldn't that be sad? No more guys. Only ladies. do you know what current theories there are for changing numbers of chromosomes? The Laminator
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coffee_addict Member (Idle past 477 days) Posts: 3645 From: Indianapolis, IN Joined: |
Edited by Lam - Double post.
This message has been edited by Lam, 07-05-2004 11:01 PM The Laminator
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coffee_addict Member (Idle past 477 days) Posts: 3645 From: Indianapolis, IN Joined: |
jar writes:
If you ever become serious about this, count me in. I have heard enough creationist arguments, both in real life and online, that I believe I can come off as more a creationist than any genuine creationist can be. I've heard more creationist straw man than some creationists I know. Actually, sometimes I can make a better creationist argument than some creationists I know just because I know the technical stuff more than them. I've often wondered if we should not get together and start our own Creationist site. I bet we can be far better than the real creationists out there because of our technical backgrounds. The Laminator
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