In the previous
Natural Limitation to Evolutionary Processes (2/14/05) thread Faith expressed a desire to better understand the nature of mutation and to further discuss some specific examples of beneficial mutations which were raised in that thread.
To that end I think we should have a mutation thread in the science forums where it belongs, and perhaps Faith can start an accompanying thread in the Theology and ID forum if she wants to develop her own ideas about how what we are discussing could fit into her own ideas about the history of life on Earth.
Mutation is not a highly specific term in and of itself. As a fundamental basis for evolution all mutation needs to be is some sort of heritable change.
Obviously the major focus of research into such things focuses on genetic mutations since we have a large number of tools for investigating and manipulating genes and a reasonable understanding of how they operate. This does not mean that genetic mutation is the be all and end all of mutation in terms of evolution, but it is certainly the best starting point.
All genetic mutations are by no means equal either, not in their extent, nature or frequency. While we can make general observations about the relative frequency of particular types of mutation, and of regions in the genome or sequences of DNA which are more prone to mutations than others, we cannot accurately predict any specific mutation occuring at a specific locus in any given organism.
The best we can do is make estimates based on the various probabilities and study populations of organisms to see how well they reflect those estimates.
Naturally the best targets for such experiments are organisms which can be grown from a single organism such as selfing plants or many types of bacteria or yeast.
For animals it is harder to get a suitable experimental species. For years
Drosophila was the standard model organism for developmental genetics, but now with the rise in transgenics mice and other species more closely related to our own are gaining prominence.
To get around the issue of not having clonal populations derived from one individual many of these populations are kept as genetically homogenous as possible by inbreeding.
Such conditions allow us to identify specific mutations when they present themselves. One of the perennial problems with the idea of reliably guaging rate of detrimental or beneficial mutations is the much more obvious nature of detrimental mutations.
We can argue to the double muscled cows come home over whether a mutated myostatin gene leading to muscular hypertrophy is really beneficial, but no one is going to quibble that a gene which leads to a total failure to develop as an embryo, or to an early death before reaching a reproductive age, is anything other than detrimental. Similarly medicine focuses specifically on syndromes and diseases we consider largely detrimental. It is only very recently that research has really taken off looking for genetic bases for things such as resistance traits to various diseases.
The only way to guage the beneficial nature of a newly arisen gene is to track its course through a population over a large number of generations. Unfortunately that has not really been tenable so far in human populations.
What can be done is to look at the prevalence of certain alleles in particular populations and make some conclusions about how selection has worked on those alleles. Naturally for biologists the origin of these alleles is ascribed to mutation, obviously that is something that Faith might wish to contend with on a thread other than this one.
This is rather a high level overview of certain isues that might be relevant to ones understanding of mutation. Ideally this thread should be a venue for others, particularly Faith, to ask specific questions about the nature of mutation and the science surrounding it.
TTFN,
WK
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