do for crown
Mourant et al. (1976) cite data on 400 Basques from Spain, of which 230 were Rh+ and 170 were Rh-.
Calculate the allele frequencies of D and d (DD individuals have the Rh+ phenotype. dd individuals have the Rh- phenotype. The phenotype of Dd is Rh+).

How many of the Rh+ individuals would be expected to be heterozygous?