Answer
A genoype is the genetic representation on chromosomes of factors (genes) that code for a trait or characteristic.
The Rh blood group antigens are coded for by a pair of genes --the dominant "D" gene and the recessive "d" gene. Consequently, a human may inherit one of three Rh genotypes --D/D, D/d or d/d . The D/D, D/d, and d/d are homozygous dominant, heterozygous, and homozygus recessive, respectively.
Work Step by Step
A phenotype is the physical or chemical expression of a gene. The phenotyes of the foregoing genotypes are:
D/D --Rh+ blood
D/d -- also Rh+ blood (because the D gene is dominant).
d/d---Rh- negative blood; the recessive gene is expressed only in the double recessive genotype.
