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Member (Idle past 1433 days) Posts: 20714 From: the other end of the sidewalk Joined: |
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Author | Topic: "Macro" vs "Micro" genetic "kind" mechanism? | |||||||||||||||||||||||||||
Brad McFall Member (Idle past 5060 days) Posts: 3428 From: Ithaca,NY, USA Joined: |
As far as I understand it you both tripped over the DIFFERNCE of orthogonalities and paralleisms but as Lam's tone thinks he can fake this I will leave to search my own posts in the matter. Best Brad.
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pink sasquatch Member (Idle past 6050 days) Posts: 1567 Joined: |
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. Actually that's a very controversial point - the Nature paper a year or so ago that was the most comprehensive examination of the Y chromosome thus far demonstrated that the Y has some tricks that give it stability - one is that it folds to "pair" with itself during time of meiotic recombination to give more stability (which has led to some masturbating Y-chromosome jokes since all other chromosomes pair with another chromosome...) Also, even if the Y chromosome did disappear in a few hundred thousand years, there would still be men, they'd just be XO instead of XY.
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RAZD Member (Idle past 1433 days) Posts: 20714 From: the other end of the sidewalk Joined: |
caffeine?
NOOOOOooooooooo.
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RAZD Member (Idle past 1433 days) Posts: 20714 From: the other end of the sidewalk Joined: |
heh - same thought occured to me. wonder where that leaves the ark scenario though ...
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RAZD Member (Idle past 1433 days) Posts: 20714 From: the other end of the sidewalk Joined: |
what I get for going from memory
isn't Przewalski's horse smaller and genetically older? 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 1433 days) Posts: 20714 From: the other end of the sidewalk Joined: |
I believe there are some species where the sex determining gene is missing.
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pink sasquatch Member (Idle past 6050 days) Posts: 1567 Joined: |
wonder where that leaves the ark scenario though ... That's easy - a pair of LUCAs... and nothing else...
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RAZD Member (Idle past 1433 days) Posts: 20714 From: the other end of the sidewalk Joined: |
there would still be men, they'd just be XO instead of XY. but would they still be wrong?
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coffee_addict Member (Idle past 505 days) Posts: 3645 From: Indianapolis, IN Joined: |
I know. I was only joking.
The Laminator
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RAZD Member (Idle past 1433 days) Posts: 20714 From: the other end of the sidewalk Joined: |
and perhaps the flood is the universe, life landing on this poor forsaken rock and saying "hey, luca what we got here ..."
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pink sasquatch Member (Idle past 6050 days) Posts: 1567 Joined: |
I figured so much - it was good for the discussion anyway. (I'm now considering making my next career move into studying sex determination for the next few years, so I've got XX, XY, XO, ZZ, ZW, on the brain...)
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RAZD Member (Idle past 1433 days) Posts: 20714 From: the other end of the sidewalk Joined: |
not XXX?
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coffee_addict Member (Idle past 505 days) Posts: 3645 From: Indianapolis, IN Joined: |
Might as well get a Ph.D. in oral sex.... Sorry, just saw one of those corny Woody Allen movie.
The Laminator
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KCdgw Inactive Member |
quote: What Johnson and other anti-evolutionists are going on about, as best as I can determine, is the phenomenon known as 'genetic homeostasis'. What this means is that populations undergoing intense directional selection (as in agricultural breeding programs) will often stop responding to selection for the trait at a certain point, accompanied with reduced fitness. Anti-evolutionists often cite Drosophila work done by Mather and Harrison, where they selected for increased numbers of abdominal bristles, as an example of limits to natural selection (and by extension, macroevolution). At some point the number did not increase beyond 36, as I recall. Anti-evolutionists jump on this, crowing that there is a limit to variation beyond which natural selection cannot go. Well, in a certain, obvious sense, they are right, but the Mather and Harrison example is not an illustration of their thesis. I Michael Lerner, the geneticist who coined the term 'genetic homeostasis' noted that it was not that the reduced fitness was caused by the population running out of variation, but that the intense selection for one trait, common in breeding progranms, disrupted gene complexes that had co-evolved over a long period of time in nature, and the reduced fitness was the response to this disruption. KC This message has been edited by KCdgw, 07-06-2004 10:10 AM
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RAZD Member (Idle past 1433 days) Posts: 20714 From: the other end of the sidewalk Joined: |
KCdgw writes: What Johnson and other anti-evolutionists are going on about, as best as I can determine, is the phenomenon known as 'genetic homeostasis'. ... the geneticist who coined the term 'genetic homeostasis' noted that it was not that the reduced fitness was caused by the population running out of variation, but that the intense selection for one trait, common in breeding progranms, disrupted gene complexes that had co-evolved over a long period of time in nature, and the reduced fitness was the response to this disruption. So the homeostasis would hold until a mutation in those co-evolved genes occurs to allow a new level to be reached? Could this be a mechanism for punctuated equilibrium? 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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