A gene is composed of two alleles. An allele can be either dominant or recessive. Suppose that a husband and​ wife, who are both carriers of the​ sickle-cell anemia allele but do not have the​ disease, decide to have a child. Because both parents are carriers of the​ disease, each has one dominant​ normal-cell allele​ (S) and one recessive​ sickle-cell allele​ (s). Therefore, the genotype of each parent is Ss. Each parent contributes one allele to his or her offspring with each allele being equally likely. Complete parts ​a) through ​c) below. ​a) Genes are always written with the dominant gene first. ​ Therefore, there are two instances the offspring could have genotype Ss​ (one if the mother contributes the dominant allele and the father contributes the​ non-dominant allele; and one if the father contributes the dominant allele and the mother contributes the​ non-dominant allele). List the other two possible genotypes of the offspring.   nothing