fixation time

Maruyama T & Kimura M 1974 A note on the speed of gene frequency changes in reverse directions in a finite population. Evolution 28:161-163.

• assuming no selection, it can be shown that under irreversible mutation from A to A', the average time until fixation of A is prolonged as compared with the case of no mutation
• this might be easily understood by considering that the frequency of A is decreased at the rate v per generation thereby prolonging the time for its frequency to reach unity
• it might be rather difficult to accept (using only common sense) that the reverse process of A decreasing its frequency from near unity to zero is equally prolonged under the same mutation pressure

• in finite populations the average length of time which it takes for an allele to increase its frequency from p to q (> p) on the way to fixation is equal to the average length of time which the same allele takes when its frequency decreases from q to p on the way to extinction