Mutations hardly ever change anything in the phenotype and when they do it is usually a disease.
Do you even have any clue whatsoever what a mutation is? Sorry, extremely stupid question, since obviously you do have no clue whatsoever.
Most of the time creationists think of physical mutations, often caused by outside factors called
mutagens which cause gross physical changes which are very obvious. Those are of absolutely no interest to evolution.
The only mutations that are of any interest at all are
genetic, and furthermore only those genetic mutations which appear in the germ cells which would make them inheritable. Any genetic mutation which is not heritable is of absolutely no interest to evolution.
The relationship of genetic mutations to changes in the phenotype is not in the least bit proportional and is very difficult to predict. You can have a lot of genetic changes with virtually no change in the phenotype, or you can have a single genetic change with a very large change in the phenotype. IOW, it is virtually impossible to make a general statement on this matter.
The genetic mutations of interest to evolution are of a few specific types (see
classification of mutations). Insertion or deletion of nucleotides (the CGTA bases in DNA) can result in frame-shift errors that completely mess up the gene, unless they occur in multiples of three (the size of a
codon). Insertion or deletion of a copy of an entire gene is far less problematic -- inserting yet another copy of a gene results in redundancy (ie, multiple alleles) and deletion or destruction (eg, via a frame-shift) of a redundant gene likewise has little effect in the phenotype.
Base substitutions are far less problematic, since in genes they only result in changes in the amino acid sequence of a protein. From class notes for the only true "balanced-treatment" creation/evolution class I've ever heard of (offered by Thwaites and Awbrey at San Diego State University in which half the lectures were by professional creationists from the then-nearby Institute for Creation Research (ICR), until escalating protests by campus Christian clubs pressured the administration to close the class (DAMNED LEFTISTS!!!!!!!!)), we find that there's a lot of wiggle room for changes in proteins' amino acid sequences. From my page,
THE "RANDOM" PROTEINS ARGUMENT:
quote:
Rather than brandying about a hypothetical protein, let's look at a specific case. In the class notes of Frank Awbrey & William Thwaites' creation/evolution class at UCSD (the Institute for Creation Research conducted half the lectures and Awbrey & Thwaites the other half), they give the example of a calcium binding site with 29 amino acid positions: only 2 positions (7%) require specific amino acids, 8 positions (28%) can be filled by any of 5 hydrophobic amino acids, 3 positions (10%) can be filled by any one of 4 other amino acids, 2 positions (7%) can be filled with two different amino acids, and 14 of the positions (48%) can be filled by virtually any of the 20 amino acids.
So a lot of base substitution mutations (at least about half of them) have no effect on the resultant protein. These are the so-called "neutral mutations" which have no effect on the phenotype and which are the basis of "molecular clocks" for making rough estimates of how long ago past populations had split off into different branches. Furthermore, they are the basis for comparing the same proteins in different species to see how closely or remotely related they are -- the picture that they paint agrees very closely with the Linnean classification system (created by a
creationist BTW), creationist false claims not withstanding (eg,
Gish's "bullfrog protein" (based solely on a joke about an enchanted prince -- No Duff!), Walter Brown's rattlesnake protein claim (same page)).
One of the things we see when base substitutions cause a gene to produce a different protein is that the old protein's functions are still provided by the other copies of that gene (again, multiple alleles). An example is the gene for lysozyme (used to attack bacteria) mutating to produce alpha-lactelbumin (a mammalian precursor to milk production -- also discussed in
The Bullfrog Affair), in which the old functionality of lysozyme continues to be covered by the other multiple genes that produce that protein.
Again, casting such pearls before swine mostly only serves to annoy the swine, but it also can serve to educate the lurkers, my intended audience.
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