As discussed in this chapter the autosomal recessive conditi

As discussed in this chapter, the autosomal recessive condition tyrosinemia type I has an observed incidence of 1 in 685 individuals in one population in the province of Quebec, but an incidence of approximately 1 in 100,000 elsewhere. What is the frequency of the mutant tyrosinemia allele in these two groups? Suggest two possible explanations for the difference in allele frequencies between the population in Quebec and populations elsewhere.

Solution

The frequency of occurrence of tyrosinemia in the first group is, 1 in 685.

As it is an autosomal recessive condition and assuming that the population is in Hardy-Weinberg equilibrium, the frequency of recessive mutant tyrosinemia allele is, q2 = 1/685; q = 0.0382

Similarly, the frequency of occurrence of tyrosinemia in the other group is, 1 in 100,000.

The frequency of recessive allele in this population is, q2 = 1/100,000, q = 0.0031

The inbreeding and genetic drift are the two reasons for the difference in allele frequencies between the population in Quebec and populations elsewhere.