[Campbell Biology P.335] Sickle-cell disease illustrates complex dominance relationships. Wh... | Practice Question

Sickle-cell disease illustrates complex dominance relationships. Which statement correctly describes these relationships at the organismal and molecular levels?

  • A: Incomplete dominance at the organismal level, codominance at the molecular level.
  • B: Codominance at the organismal level, incomplete dominance at the molecular level.
  • C: Complete dominance at both the organismal and molecular levels.
  • D: Recessive at the organismal level, codominant at the molecular level.

Explanation

The text explicitly states: 'at the organismal level, the normal allele is incompletely dominant to the sickle-cell allele.' It also says, 'At the molecular level, the two alleles are codominant; both normal and abnormal sickle-cell hemoglobins are made in heterozygotes.' This demonstrates how dominance can be context-dependent.