[asa] How big a deal is homology?

This is a question for those on the list who know more molecular genetics than I do (almost everyone!). Now that the human genome has been sequenced, as well as that of several other organisms, sequences can be compared and checked for similarity. Much has been made of the 95 odd percent similarity between the genomes of humans and chimps. And of course the 80 odd percent similarity between mice and humans. Anti-evolutiuonists point out that the similarity is only 95 or so percent, not the 98% once claimed. Ha! And of course mice are even less similar. But isn't the problem that there is any similarity at all? Aren't family relationships demonstrated by matching identical sequences of DNA that are long enough to rule out coincidence? And aren't these same types of similarities found linking different species, genera, families etc, such as humans, chimps and mice? Maybe I'm demonstrating my ignorance of molecular genetics. Does 95% similarity between human and chimp DNA mean !
 that 95% of the sequences are similar? I ask because I am involved in discussion with someone who is skeptical of DNA comparisons.

Brent

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Received on Tue Mar 27 12:16:24 2007