What is required for a person to have sickle-cell disease? a. the person is homozygous and has malaria b. the person is heterozygous and has malaria c. the person is heterozygous for the trait d. the person is homozygous for the trait

           The correct option is D, because a person having sickle cell anemia  must be homozygous for the trait.

Explanation:

                  Sickle cell disease is autosomal inherited disease. In this disease the shape of red blood cell change from round to crescent shape, as a result it become unable to carry oxygen because it can not pass through capillaries. When Glutamine amino acid is replaced by Valine the shape of hemoglobin become sickle shaped. 

Genetics of Sickle cell anemia:

                                                  This disease appears in homozygous recessive from. Genes for sickle cell is represented by  "S" while for normal it is represented by capital "A". If a carrier man marry a carrier woman then 50% of child will be sickle celled, 25% will be normal and 25% will be carrier for disease as shown in the figure