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Author Topic:   Directly Observed Mutation
Inactive Member

Message 27 of 50 (154903)
11-01-2004 2:28 PM
Reply to: Message 25 by RustyShackelford
11-01-2004 2:22 PM

Re: micro - macro
I've heard variation of color in plants and animals in adaptation to environment isn't caused by new mutation.
This is very true. In humans, skin color is determined by the number of copies of a certain gene. What we are talking about is new mutations previously not found in the gene pool of a species. One example is hemoglobin C, a new type of hemoglobin created by a single mutation. This protein allows resistance to malara without the side effects associated with sickle cell anemia (hemoglobin S). Right now, this gene is found in a very small population where the mutation first occured. It is expected to spread rapidly through Africa in areas with endemic malaria. This is evolution in action.

This message is a reply to:
 Message 25 by RustyShackelford, posted 11-01-2004 2:22 PM RustyShackelford has replied

Replies to this message:
 Message 31 by RustyShackelford, posted 11-01-2004 2:31 PM Loudmouth has replied

Inactive Member

Message 40 of 50 (154940)
11-01-2004 3:08 PM
Reply to: Message 31 by RustyShackelford
11-01-2004 2:31 PM

Re: micro - macro
Loudmouth, but if the people haven't mutated, then they haven't evolved, right?
They have evolved. They acquired a new gene through mutation (hemoglobin C) that is selected for by the environment. This is evolution in action. They are still human, but they are different than the humans that came before them.
Edited to add recent research on hemoglobin C:
J Infect Dis. 2004 Sep 1;190(5):1006-9. Epub 2004 Jul 26. Related Articles, Links
Hemoglobin C and resistance to severe malaria in Ghanaian children.
Mockenhaupt FP, Ehrhardt S, Cramer JP, Otchwemah RN, Anemana SD, Goltz K, Mylius F, Dietz E, Eggelte TA, Bienzle U.
Institute of Tropical Medicine, Medical Faculty Charite, Humboldt University, Berlin, Germany.
Hemoglobin (Hb) C has been reported to protect against severe malaria. It is unclear whether relative resistance affects infection, disease, or both. Its extent may vary between regions and with disease pattern. We conducted a case-control study of children with severe malaria, asymptomatic parasitemic children, and healthy children in Ghana. HbAC did not prevent infection but reduced the odds of developing severe malaria and severe anemia. Protection was stronger with HbAS. The frequencies of HbCC and HbSC decreased, from healthy children to asymptomatic parasitemic children to children with severe malaria. These data support the notion that natural selection of HbC occurs because of the relative resistance it confers against severe malaria but argue against the notion that HbC offers resistance to infection.
J Evol Biol. 2004 Jan;17(1):221-4. Related Articles, Links
Estimation of relative fitnesses from relative risk data and the predicted future of haemoglobin alleles S and C.
Hedrick P.
School of Life Sciences, Arizona State University, Tempe, AR 85287, USA.
Epidemiological studies of genetic differences in disease susceptibility often estimate the relative risks (RR) of different genotypes. Here I provide an approach to calculate the relative fitnesses of different genotypes based on RR data so that population genetic approaches may be utilized with these data. Using recent RR data on human haemoglobin beta genotypes from Burkina Faso, this approach is used to predict changes in the frequency of the haemoglobin sickle-cell S and C alleles. Overall, it generally appears that allele C will quickly replace the S allele in malarial environments. Explicit population genetic predictions suggest that this replacement may occur within the next 50 generations in Burkina Faso. emphasis mine
This message has been edited by Loudmouth, 11-01-2004 03:13 PM

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 Message 31 by RustyShackelford, posted 11-01-2004 2:31 PM RustyShackelford has not replied

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