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Author Topic:   Favorable Mutations? Help me!!
Coragyps
Member (Idle past 735 days)
Posts: 5553
From: Snyder, Texas, USA
Joined: 11-12-2002


Message 11 of 56 (54221)
09-06-2003 6:20 PM


To lift a post of my own from a different forum, where the canarn of "no new information" is actually the subject of the thread, but the example is one of my favorites. I think of Hemoglobin C as sort of a "sickle-cell lite."
------------
Ref: Nature, vol 414, pp 305-308 (2001) - "Haemoglobin C protects against clinical Plasmodium falciparum malaria" , by D Modiano et al. It's not online, to my knowledge, except by paid subscription.
Normal human hemoglobin ("HbA") is coded for by DNA which reads, as the 16th through 18th positions of a certain gene, GAA. This codon tells a cell's protein factory to put the amino acid glutamate at the sixth spot along the peptide that will become the beta chain of your or my hemoglobin. However, in a large number of West Africans, particularly the Mossi of Burkina Faso, this speck of DNA reads AAA. The distribution of folks with this variant looks like a bull's-eye: lots of the gene in one area of Burkina Faso, and fewer and fewer people with it as you move away from that center. The distribution is consistent with the idea that one person had the mutation about a thousand years ago, and that it spread through his or her descendants since. (Most people weren't terribly mobile in that area until nearly modern times - at least until the slave trade started.)
Now this DNA change alters that sixth amino acid on the beta chain of hemoglobin to lysine, making HbC. Most people with hemoglobin C never know it - some have mild anemia, gallstones, or spleen problems. But Modiano's paper documents that Mossi children that have both genes for HbC are 7% as likely to develop malaria as their classmates who have boring old HbA. 7% as likely to get the disease that kills a couple of million kids in West Africa every year. And that's because their genome has the information to make a protein that has one amino acid that's different from the one in their neighbors, and in their ancestors, too, if you go back a ways. New information. Useful new information. (You will agree that being able to make two different proteins is "more information" than being able to make only one, won't you? Kids in the study that had the AC genotype - that had both HbA and HbC in their blood - had a 29% reduction in their chance of getting malaria.) New, useful, "information" from a mutation.
Now a footnote: if your DNA reads GUA instead of GAA in this position, you get a valine in position 6 and have sickle-cell trait - the result of a different mutated hemoglobin called HbS. This protects against malaria, too, but the side effects can be severe, including fatal, especially if you have both genes for HbS. This, too, is "new information" - a different protein is being made.

  
Coragyps
Member (Idle past 735 days)
Posts: 5553
From: Snyder, Texas, USA
Joined: 11-12-2002


Message 15 of 56 (54594)
09-09-2003 3:44 PM
Reply to: Message 13 by Fred Williams
09-09-2003 2:48 PM


Re: Nylon is just pantyhose
The pertinent question to ask is, what evidence exists where the mutated type is more viable than the parent type in a normal environment?
Is West Africa, with its high incidence of malaria, a "normal environment?"

This message is a reply to:
 Message 13 by Fred Williams, posted 09-09-2003 2:48 PM Fred Williams has not replied

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Coragyps
Member (Idle past 735 days)
Posts: 5553
From: Snyder, Texas, USA
Joined: 11-12-2002


Message 33 of 56 (57525)
09-24-2003 5:34 PM
Reply to: Message 31 by Fred Williams
09-24-2003 2:30 PM


Re: A big goose egg
Mr Williams: any comment on posts 11 and 15 of this thread?

This message is a reply to:
 Message 31 by Fred Williams, posted 09-24-2003 2:30 PM Fred Williams has replied

Replies to this message:
 Message 35 by Fred Williams, posted 09-24-2003 8:23 PM Coragyps has replied

  
Coragyps
Member (Idle past 735 days)
Posts: 5553
From: Snyder, Texas, USA
Joined: 11-12-2002


Message 39 of 56 (57776)
09-25-2003 1:04 PM
Reply to: Message 35 by Fred Williams
09-24-2003 8:23 PM


Re: A big goose egg
Is West Africa, with its high incidence of malaria, a "normal environment?"
--------------------------------------------------------------------------------
NO!
And just where is there a "normal environment" on this planet, then? Luxembourg? Itta Bena, Mississippi? What makes West Africa "abnormal?"

This message is a reply to:
 Message 35 by Fred Williams, posted 09-24-2003 8:23 PM Fred Williams has not replied

  
Coragyps
Member (Idle past 735 days)
Posts: 5553
From: Snyder, Texas, USA
Joined: 11-12-2002


Message 43 of 56 (58628)
09-29-2003 8:19 PM
Reply to: Message 35 by Fred Williams
09-24-2003 8:23 PM


Re: A big goose egg
Mr Williams: Give me a example or two of "normal environments," and explain, please, without references to Caddyshack, why Burkina Faso is not one.

This message is a reply to:
 Message 35 by Fred Williams, posted 09-24-2003 8:23 PM Fred Williams has not replied

  
Coragyps
Member (Idle past 735 days)
Posts: 5553
From: Snyder, Texas, USA
Joined: 11-12-2002


Message 54 of 56 (162027)
11-21-2004 10:45 AM
Reply to: Message 53 by jjjj
11-21-2004 7:30 AM


Re: Preteen model in pantyhose and stockings. Free beautiful photos
Pantyhose and stockings? Must be cold there.....

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 Message 53 by jjjj, posted 11-21-2004 7:30 AM jjjj has not replied

  
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