Abstract

BACKGROUND:

In populations with alpha(+)-thalassemia gene deletion, the practice of consanguineous marriages is common.

AIM:

The study explored the impact of consanguinity (inbreeding) on the selection of alpha(+)-thalassemia genotypes in a computer model.

METHOD:

In a population under selection pressure from malaria, a single protective mutation (-alpha/alphaalpha genotype) was introduced among normal genotypes (alphaalpha/alphaalpha), and mating allowed to proceed. Heterozygote (-alpha/alphaalpha) and homozygote (-alpha/-alpha) children were 1.5 and 2.5 times more likely to survive malaria than those with normal genotypes. Using different coefficients of inbreeding (F, range 0-0.12), we examined the effect of population size, and the mean number of generations required for the homozygote frequency to reach 0.5.

RESULTS:

On average, consanguineous populations were larger than randomly mating populations and the size was directly proportional to F. In more inbred populations,-alpha/-alpha homozygotes reached a frequency of 0.5 faster than in less inbred populations. As the frequency of the alpha(+)-thalassemia allele in a population increases, however, the positive effect of inbreeding on the population growth decreases.

CONCLUSION:

Under selection pressure from malaria, consanguinity may increase the speed of selection of-alpha/-alpha homozygotes and provide an advantage regarding population growth over non-consanguineous populations.