Question

Genetics - Question 3

Defining heterozygosity, H, as the probability that two sequences randomly sampled from a population are different, for a diploid species with a population size of N = 1000 individuals and initial heterozygosity H0 = 0.5 ; a neutral mutation rate of u = 10^-9,

1. What is the rate of substitution with the above mutation rate? Explain. [5 marks]
2. If, for beneficial mutation A1 the selection coefficient is s = 0.01, what is the
   probability of substitution for a new beneficial mutation? [3 marks]
3. If, for deleterious mutation A2 the selection coefficient is s = 0.001, what is the probability of substitution for a new deleterious mutation? [3 marks]

Answer 1

rate of substitution will be 10^-9

Substitution rate is defined as the rate at which mutation is fixed in a population. If rate of neutral mutation is per individual per generation is u, total mutation in generation will be Nu (where N is number of individual).  Neutral mutations are the mutations which have neither deleterious nor advantageous effect. All mutations have equal chance of reaching substitution, therefore, probability of each mutation to become substitution is 1/N.

Rate of substitution= Number of new mutations in each generation (Nu) X probability of mutation to become substitution (1/N).

= Nu X (1/N) = u

Therefore,in neutral mutations, rate of substitution = rate of mutation.