Assuming we have 1000 DNA residues at random, after time deltaT the sequences dffer from the original in 33% of the sites. Assuming that the sequence evolves under Jukes-Cantor, what is the expected number of substitutions per site? When deltaT becomes very large (infinity), how many sites will on average have the same nucleotide?
2007-02-07 03:34:33 · 1 answers · asked by motobecane 2 in Science & Mathematics ➔ Biology
Without seeing the context in which this question is asked I'm not sure if I'm answering correctly, so don't take my word on it if this doesn't make sense to you.
Jukes-Cantor is a model of sequence evolution where there is an equal probability for different types of sequence mutation. Therefore, if 33% of the sites change, then the expected number of substitutions per site is 1/3.
Over a long deltaT, due to multiple hits per site, on average 1/4, or 250, of the sites will have a nucleotide that's the same as the starting nucleotide state. This is an artifact of only having 4 possible character states.
2007-02-07 07:05:03 · answer #1 · answered by plantgirl 3 · 0⤊ 0⤋