quote:
Simple is good. Let's use a cartoon organism. It has a mutation rate of 1x10^-9/bp/gen and a genome of 1 billion base pairs, so on average there is 1 mutation per generation. Half of its mutations are single-base substitutions, and half are large indels. Let's look at a copy of the genome from each branch just one generation after they split. In that 1 generation, one copy acquired one single-base substitution. The other copy acquired an insertion of 10 million base pairs. As a result, the genomes now differ by 10,000,001 base pairs, or just over 1%.
Do you read any of my citations? Think average...
This would be a problem if mutation rates were as simple as you think they are. From my citation:
Mutation Rate = # of mutations observed [30] (# of experimental lines [198]) x (average # of generations [339]) x (average # of base pairs sequenced [~21,000])
The citation I showed you directly counted base pairs in the indel over an average of measurements. Mutation rates are considered in the citation as averages. One case won’t cut it.
Examining the DNA sequences from their experimental animals (a total of over 4 million base pairs!), and comparing them with the controls, turned up a total of 30 mutations.
17 of these were insertions or deletions ("indels')
◦ 7 in exons all but 2 of which produced frameshifts and a premature STOP codon.
◦ 10 in introns or between genes
13 of these were single base substitutions ("point" mutations)
◦ 3 in exons : one "silent" producing a synonymous codon; two that changed the encoded amino acid.
◦ 10 in introns or between genes
I hope most who read this got over the indel being counted as one mutation a few posts back
Calculating Mutation Rate
From these results I have pooled their data to calculate an approximate rate at which spontaneous mutations occur throughout the genome.
Mutation Rate = # of mutations observed [30] (# of experimental lines [198]) x (average # of generations [339]) x (average # of base pairs sequenced [~21,000])
yielding a rate of 2.1 x 10-8 mutations per base pair per generation.
The total C. elegans genome contains some 108 base pairs so this tells us that two new germline mutations occur somewhere in each of C. elegans's two haploid genomes in each generation.
http://users.rcn.com/...Mutations.html#MeasuringMutationRate
It is always important to read citations when continuing an argument.
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