Are functional proteins rare?
- Thread starter bob b
- Start date
eisenreich
New member
Do you disagree with the first three paragraphs from Case 4? If so, why is your view different than what the poster asserts?bob b said:
Looks like his source was this book:
Endless Forms Most Beautiful: The New Science of Evo Devo and the Making of the Animal Kingdom (Hardcover)
"Every animal form is the product of two processes--development from an egg and evolution from its ancestors," writes Sean B. Carroll in his introduction to Endless Forms Most Beautiful. The new science of "evo devo"--or evolutionary developmental biology--examines the relationships between those two processes, embryonic development and evolutionary changes, despite their radically different time scales."
eisenreich said:
Case #4 paragraph 3
The author starts out fine by appealing to laboratory experiments. I read such cases carefully, although isolated and perhaps non-conclusive examples are not very persuasive in the grand scheme of things, for evolution makes very grandiose claims and should properly be supported by very strong evidence to be considered science.
But in the next paragraph the author of case#4 makes a claim that could never be supported by scientific evidence. He says that essentially everything of significance regarding proteins happened prior to the Cambrian, where there is virtually no significant evidence at all!! This claim reminds me of Gould's claim that macroevolution typically happens so quickly that it has left no trace in the fossil record.
Such claims as these are not science.
From EurekaAlert:
Evolution follows few of the possible paths to antibiotic resistance
Bacteria gain resistance from only a handful of 120 possible five-step mutational paths in a key gene
CAMBRIDGE, Mass. -- Darwinian evolution follows very few of the available mutational pathways to attain fitter proteins, researchers at Harvard University have found in a study of a gene whose mutant form increases bacterial resistance to a widely prescribed antibiotic by a factor of roughly 100,000. Their work indicates that of 120 harrowing, five-step mutational paths that theoretically could grant antibiotic resistance, only about 10 actually endow bacteria with a meaningful evolutionary advantage. The research is published in the journal Science.
"Just as there are many alternate routes one might follow in driving from Boston to New York, one intrinsic property of DNA is that very many distinct mutational paths link any two variants of a gene," says lead author Daniel M. Weinreich, a research associate in Harvard's Department of Organismic and Evolutionary Biology. "Although this fact has been recognized for at least 35 years, its implications for evolution by natural selection have remained unexplored. Specifically, it is of great interest to determine whether natural selection regards these many mutational paths equivalently."
Weinreich and colleagues generated a series of mutants found along all 120 possible mutational trajectories involving the gene coding for the enzyme beta-lactamase, which in altered form can serve to inactivate antibiotics including penicillin and cefotaxime. Analyzing how well each variant protected host Escherichia coli cells against treatment with various concentrations of antibiotic, the scientists found that only a very small fraction of these pathways confer ever-increasing resistance in pathogenic microbes, and are therefore relevant to natural selection.
Resistance-granting mutations of beta-lactamase occur in a five-step process, with the 120 possible mutational paths representing all the possible ways in which these five point mutations can occur. Fully 102 of the 120 trajectories are inaccessible to natural selection because they create intermediates that are no more fit than the original gene, and of the remaining 18 Weinreich and colleagues observed that only about half actually had a significant probability of evolutionary occurrence.
"To be followed by an evolving population, natural selection requires that antibiotic resistance increase with each mutation," Weinreich says. "In contrast, most mutational paths of the enzymatic variant we examined fail to continuously increase resistance. Importantly, this is not a reflection of the fact that many more mutations reduce biological function than improve it, because in the present case each mutational path is composed exclusively of mutations known jointly to improve resistance."
Weinreich argues that this finding likely applies to most protein evolution, not just the beta-lactamase enzyme.Although many mutational paths lead to favored variants, only a very small fraction are likely to result in continuously improved fitness and therefore be relevant to the process of natural selection.
------
Like none?
Evolution follows few of the possible paths to antibiotic resistance
Bacteria gain resistance from only a handful of 120 possible five-step mutational paths in a key gene
CAMBRIDGE, Mass. -- Darwinian evolution follows very few of the available mutational pathways to attain fitter proteins, researchers at Harvard University have found in a study of a gene whose mutant form increases bacterial resistance to a widely prescribed antibiotic by a factor of roughly 100,000. Their work indicates that of 120 harrowing, five-step mutational paths that theoretically could grant antibiotic resistance, only about 10 actually endow bacteria with a meaningful evolutionary advantage. The research is published in the journal Science.
"Just as there are many alternate routes one might follow in driving from Boston to New York, one intrinsic property of DNA is that very many distinct mutational paths link any two variants of a gene," says lead author Daniel M. Weinreich, a research associate in Harvard's Department of Organismic and Evolutionary Biology. "Although this fact has been recognized for at least 35 years, its implications for evolution by natural selection have remained unexplored. Specifically, it is of great interest to determine whether natural selection regards these many mutational paths equivalently."
Weinreich and colleagues generated a series of mutants found along all 120 possible mutational trajectories involving the gene coding for the enzyme beta-lactamase, which in altered form can serve to inactivate antibiotics including penicillin and cefotaxime. Analyzing how well each variant protected host Escherichia coli cells against treatment with various concentrations of antibiotic, the scientists found that only a very small fraction of these pathways confer ever-increasing resistance in pathogenic microbes, and are therefore relevant to natural selection.
Resistance-granting mutations of beta-lactamase occur in a five-step process, with the 120 possible mutational paths representing all the possible ways in which these five point mutations can occur. Fully 102 of the 120 trajectories are inaccessible to natural selection because they create intermediates that are no more fit than the original gene, and of the remaining 18 Weinreich and colleagues observed that only about half actually had a significant probability of evolutionary occurrence.
"To be followed by an evolving population, natural selection requires that antibiotic resistance increase with each mutation," Weinreich says. "In contrast, most mutational paths of the enzymatic variant we examined fail to continuously increase resistance. Importantly, this is not a reflection of the fact that many more mutations reduce biological function than improve it, because in the present case each mutational path is composed exclusively of mutations known jointly to improve resistance."
Weinreich argues that this finding likely applies to most protein evolution, not just the beta-lactamase enzyme.Although many mutational paths lead to favored variants, only a very small fraction are likely to result in continuously improved fitness and therefore be relevant to the process of natural selection.
------
Like none?