Question

sickle cell anemia is a condition that affects the shape of a red blood cell. an unaffected individual can be represented with the genotype aa. an affected individual can be represented with the genotype ss. individuals that are carriers have the genotype as. which is the best description of sickle cell anemia?
multiple alleles
incomplete dominance
homozygous recessive
heterozygous dominant

Explanation:

• Multiple alleles: There are only two alleles (A and S) involved, not more than two, so this is incorrect.
• Incomplete dominance: When a heterozygote (AS) shows an intermediate phenotype (carrier state, not fully unaffected like AA nor fully affected like SS), this is characteristic of incomplete dominance.
• Homozygous recessive: While SS is homozygous recessive for the affected trait, the question is about the overall genetic description of the condition which is better explained by incomplete dominance as it involves the interaction of alleles in heterozygotes.
• Heterozygous dominant: There is no indication of a simple dominant - recessive relationship where heterozygote shows the dominant phenotype fully. Here, the heterozygote (AS) has an intermediate (carrier) state.

Answer:

incomplete dominance