Keisha and Jerome each have a sibling with sickle-cell disease. Neither Keisha nor Jerome nor any of their parents have the disease, and none of them have ever been tested to see if they carry the sickle-cell allele. Based on this incomplete information, calculate the probability that if this couple has a child, the child will have sickle-cell disease.

The answer would be c, white eyes are homozygous recessive. in the early 1900s, morgan conducted several experiments with vinegar  flies (drosophila). one  sample revealed an anomaly: a  white-eyed, single male fly. he attempted to breed this fly with the typical red-eyed females. the offspring were all red-eyed. using flies from this new generation (brother-sister pairs)  produced some red-eyed and a few white-eyed flies. the white-eyed were all male. in later experiments, he was able to produce white-eyed females. this proved that white eyes are not lethal to either sex (ruling out a and b). since the percentage of white eyes to red eyes is so low, white eyes are not a dominant trait. it would be a recessive trait. 

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