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Nuggets from 'How to Clone a Mammoth' - Yazata - Jun 24, 2015
I checked 'How to Clone a Mammoth' (by Beth Shapiro, 2015, Princeton U. Press) out from the library and have been slowly reading it the last few weeks. There's lots of interesting stuff in there. I'm going to use this thread to post about things that caught my eye.
The Species Concept (p. 28).
"A species tends to be defined as an evolutionary lineage that is reproductively isolated from all other evolutionary lineages... Individuals belonging to different species cannot mate. Or if they do, the offspring that are born either do not survive into adulthood or cannot have offspring themselves."
This definition is apparently fairly recent, originating with Ernst Mayr in 1942. It's found in most textbooks. But it doesn't always work that way in real life.
Shapiro points out that polar bears and brown bears are considered separate species, but they can mate and produce fertile offspring. Dogs, wolves and coyotes are considered separate species but they frequently interbreed. Cows, bison and yaks can all interbreed and produce fertile offspring.
Genome Dimensions (p. 41)
Quantities of DNA are typically measured in terms of base-pairs (the rungs on the DNA double-helix ladder). The human genome has about 3.2 billion base pairs, organized into 23 chromosomes.
Compare that to the loblolly pine genome, which has roughly 22.2 billion base pairs in 12 huge chromosomes. Or the carp genome which has 1.7 billion base pairs in 100 little chromosomes.
So my take-away is that the number of chromosomes isn't really an indicator of how much DNA is present, nor is the amount of DNA proportional to the complexity of the organism. (These pine trees have 7x as much DNA as a human? Why? What's it doing?)
RE: Nuggets from 'How to Clone a Mammoth' - C C - Jun 24, 2015
(Jun 24, 2015 03:54 AM)Yazata Wrote: So my take-away is that the number of chromosomes isn't really an indicator of how much DNA is present, nor is the amount of DNA proportional to the complexity of the organism. (These pine trees have 7x as much DNA as a human? Why? What's it doing?)
Supposedly pines, cedars, firs, and spruces don't remove repetitive DNA sequences that lack function as efficiently as other plants and animals do. So that their genomes have accumulated lots of useless padding. However, some conifers still have 6000+ more functional genes than humans.
The view of "junk DNA" has changed over the years. A significant percentage of those bases may actually be devoted to regulating the more familiar work of the protein-coding ones. But there's such an enormous amount of baggage in these trees that it seems safe to assume that most of it really is impotent.
Perhaps the "Sunday" mainstream might construe the situation as indicating God really does like Christmas trees and pagan-converted holidays after all. Accordingly annoyed by the Jewish-mimicking 7th-day rivals and their OT holy days. But then the puzzling over-affection for beetles still remains.