Okay, I’ve gotten the genetics textbook and have started reading it. You’re correct in saying the book won’t help much in our discussion on creation/evolution other than giving us a foundation for discussing genetics.
I was hoping the book would say something about d- and l-isomers, but I don’t think it does—at least I haven’t found it yet. It then occurred to me that I might be more likely to find this in an organic or biochemistry textbook. Since I still have some of my old textbooks, I looked in them and found it quite easily.
The book’s definition of evolution: “genetic change among members of a population.” p.663 According to this definition, any change would be considered evolution. This definition conflates adaptation (variation within a kind, which I have no problem with) and macroevolution (change from one kind to another, such as monkey to man, or even prokaryotes to eukaryotes). The textbook appears to do an excellent job of explaining adaptation within a framework of genetics. On the other hand, it seems to be a bit lacking in explaining the ‘monkey to man’ type of evolution within the framework of genetics. Of course, the study of macroevolution primarily involves forensic science, while this textbook focuses on genetics from an empirical perspective.
An excerpt from chapter 17, on mutations: “Mutation is a fact of life. Our DNA is continually assaulted by spontaneously arising and environmentally induced mutations. The fact that most are detrimental is evidenced by the number of mechanisms that cells possess to reduce the generation of errors in DNA and to repair those that do arise.” (p.500)
So living organisms possess multiple mechanisms to correct mutations. Yet the build up of mutations is supposed to be a driving force in Darwinian evolution. I’ve not yet discovered from the book how the forward movement of Darwinian evolution is supposed to have overcome the resistance to change evidenced by the corrective mechanisms.
My results (Table 4) confirm several generally accepted facts about human spontaneous mutation: 1) well over 90% of all mutations are single nucleotide substitutions [Giannelli et al., 1999; Nachman and Crowell, 2000], 2) CpG context increases substitution rate by ~1 order of magnitude [Sommer, 1995; Nachman and Crowell, 2000], and 3) deletions are ~3 times more common than insertions [Gu and Li, 1995] so that mutation shrinks human genome by ~1 nucleotide per generation [Petrov, 2001]. [italics are mine] ...Kondrashov, A. S. 2003. Direct estimate of human per nucleotide mutation rates at 20 loci causing Mendelian diseases. Human Mutation. 21 (1): 12-27.
The results reported here imply, in agreement with previous estimates [Vogel and Rathenberg, 1975; Kondrashov, 1988], that the total number of new mutations per diploid human genome per generation is ~100 (1.8 x 10tothe -8 x 2 x 3.2 x 10 to the 9=115). [couldn’t figure out how to make it write the correct symbols]
What I find interesting in the above study is the statement that mutations shrink human genome over time. This flies in the face of the Darwinian idea that mutations increase genetic information and complexity. If Darwinian evolution actually occurred, it would have had to overcome the loss of genetic information caused by mutations. [This study also seems to disagree with the genetics textbook in saying that most mutations are substitutions, while the genetics book states that insertions and deletions are more frequent (p.477). Since most of the references for chapter 17 are older than this article, this article is probably based on newer information than what was available for the book.]
In chapter 19, on genomics: “The reduced DNA content, fewer functional genes, and the large number of pseudogenes suggest that, evolutionarily, the genome of M. Leprae has undergone massive decay through time, losing DNA and acquiring mutations that have inactivated many of its genes... Regardless of the mechanism for gene inactivation and loss, this genomic decay helps explain some of the bacterium’s unique properties. Genes for many metabolic enzymes and structural proteins have been lost, which may explain why the bacteria cannot be cultured on synthetic media containing traditional carbon sources; it may also account for the bacterium’s slow growth.” (p. 553)
Here, we’re talking about the degeneration over time of the genome of the leprosy bacterium. I would call this genetic entropy. The book says that this particular genome has deteriorated over time. This poses a number of questions: How did this bacteria evolve forward from non life or a simpler organism to become the leprosy bacterium? What made this forward movement (from less complex to more complex) stop and begin to move backward (degenerate)? If this genome has degenerated over time, why wouldn’t we expect any other genome to degenerate over time? The Kondrashov study certainly indicates that the human genome has been degenerating (which agrees with the book on genetic entropy). What scientists routinely observe is degeneration over time. Where is the observation of the monkey to man sort of Darwinian evolution?
This is enough to begin with. Since you’ve had more time to read the book than I have, perhaps you’ve already found answers to some of my questions. And I’m sure you have questions of your own. I’m looking forward to hearing what you have to say. :o)
On a lighter note, snow is coming our way again—we’ve had quite a bit of cold and windy weather this winter. Of course, I don’t mind as long as I’m inside with a cheery fire in the fireplace. We’ve been keeping the bird feeders full, and it has been fun seeing all the different kinds of birds that show up.
Susan
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