If one individual in 1,000,000 has a genetic disease caused by a recessive Mendelian allele, roughly what fraction of individuals in a randomly mating population are heterozygous carriers of this disease allele.

Normal Mendellian genetics uses the law of independent assortment and law of segregation. The law of independent assortment: This means that there is a fair chance of either or allele to be passed on with the same frequency. Then law of independent assortment: Different alleles of different traits will segregate independently of each other and are not linked to the other.

Assuming that the disease is not fatal in anyway. If the gene is recessive this means that there must be two alleles present this means the one or both parents must have this allele. In this case a random sampling of the population should be twice the number of those that have the trait assuming the segregation is 1:2:1 for normal, heterozygous, mutation therefore the answer is 2 million