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Author Topic:   A question about evolution
AZPaul3
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Posts: 8513
From: Phoenix
Joined: 11-06-2006
Member Rating: 5.3


Message 55 of 70 (799383)
02-09-2017 6:53 PM
Reply to: Message 54 by Coyote
02-09-2017 10:26 AM




This message is a reply to:
 Message 54 by Coyote, posted 02-09-2017 10:26 AM Coyote has seen this message but not replied

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 Message 57 by CRR, posted 03-03-2017 4:57 AM AZPaul3 has replied

  
AZPaul3
Member
Posts: 8513
From: Phoenix
Joined: 11-06-2006
Member Rating: 5.3


(2)
Message 59 of 70 (801078)
03-03-2017 6:54 AM
Reply to: Message 57 by CRR
03-03-2017 4:57 AM


Re: Step 2
However I have read that red hair is due to a defect in the MC1R gene so there would be a loss of genetic information in that case.
A loss of information or different information like with skin color? Is it really a defect or just a difference? A different allele? I think your use of the word "defect" is intentionally loaded.
Evolution did it.
Yes, it did. No Easter Bunny necessary. Glad you agree.


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 Message 57 by CRR, posted 03-03-2017 4:57 AM CRR has replied

Replies to this message:
 Message 60 by CRR, posted 03-03-2017 7:01 AM AZPaul3 has replied

  
AZPaul3
Member
Posts: 8513
From: Phoenix
Joined: 11-06-2006
Member Rating: 5.3


Message 62 of 70 (801086)
03-03-2017 7:13 AM
Reply to: Message 60 by CRR
03-03-2017 7:01 AM


Re: Step 2
We all have the gene that is linked most strongly to red hair, MC1R. It is just that most red haired people have different versions of this gene compared to people without red hair.
And there are lots of different versions of MC1R out there.
Same source.
A different allele of the same gene. No information loss. An information difference. Different proteins resulting from the different nucleotide sequences.


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 Message 65 by caffeine, posted 03-04-2017 8:53 AM AZPaul3 has replied

  
AZPaul3
Member
Posts: 8513
From: Phoenix
Joined: 11-06-2006
Member Rating: 5.3


Message 66 of 70 (801218)
03-04-2017 10:12 AM
Reply to: Message 65 by caffeine
03-04-2017 8:53 AM


Re: Step 2
The known mutations which lead to the 'red hair' alleles of MC1R are all loss of function mutations. They produce a receptor protein which is broken, in a sense, and so where the wild type would perform its role of promoting melanin production, the red hair variants don't.
Is that right?
Or, do the major variants of MC1R cause the melanocortin 1 receptor to stimulate the melanocytes into eumelanin production while the minor variants of MC1R block the melanocortin 1 receptor from stimulating eumelanin production causing the melanocytes to make mostly pheomelanin instead?
Do you really consider the minor variants of MC1R to be "broken, in a sense"?
This may seem a semantic quibble, but it does get to the very heart of CRR's misunderstanding of genetics as a whole.
And, no, I do not believe you would call this a "loss" of genetic information.
So, again, no information loss. An information difference. Different proteins resulting from the different nucleotide sequences. Different proteins having different effects upon the system.
And, as often happens with evolution, some of the minor variants convey some advantage in an environment and become the major variants in a population.
CRR is not completely off on this one.
Since he wouldn't know why, I'll disagree.
Edited by AZPaul3, : No reason given.
Edited by AZPaul3, : affect/effect. I still have trouble with this.


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 Message 65 by caffeine, posted 03-04-2017 8:53 AM caffeine has replied

Replies to this message:
 Message 67 by CRR, posted 03-04-2017 6:31 PM AZPaul3 has replied
 Message 70 by caffeine, posted 03-05-2017 4:06 PM AZPaul3 has seen this message but not replied

  
AZPaul3
Member
Posts: 8513
From: Phoenix
Joined: 11-06-2006
Member Rating: 5.3


(4)
Message 69 of 70 (801293)
03-04-2017 10:04 PM
Reply to: Message 67 by CRR
03-04-2017 6:31 PM


Re: Step 2
As humans migrated north, the absence of high levels of solar radiation in northern Europe and Asia relaxed the selective pressure on active MC1R, allowing the gene to mutate into dysfunctional variants without reproductive penalty, then propagate by genetic drift.
Poor presentation and word choice on the part of the Wiki author.
The variants of MC1R are fully functional, they just function in a different way. Where the MC1R gene in the, shall I say, standard form produced proteins that stimulate the melanocytes into eumelanin production (the darker brown/black melanin) several variants produce proteins that disrupt and lessen that production allowing more production of pheomelanin (the yellow/red melanin).
As Coyote points out in his message such variants proved beneficial for migrants into northern climes (increases in vital photo chemical production). And by beneficial we mean fitter for the environment they had moved into and fitness is measured in differential reproductive success. Nothing dysfunctional about a gene that lets a population make more successful babies.
Still no loss of information. Different information doing different stuff.
Edited by AZPaul3, : No reason given.


This message is a reply to:
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