Which of the following disease states is known to be caused by homozygous recessive genes in an individual?
A. Pellagra.
B. Beriberi.
C. Hypertension.
D. Sickle-cell anemia.
Sickle-cell anemia is a condition where homozygous recessive genes are necessary for full development of the disease. If an individual has heterozygous recessive genes for the disease, that individual only shows sickle-cell trait, but not the fully developed disease.