An allele that masks the recessive allele is called the

• A. Haploid cell
• B. Dominant
• C. Recessive
• D. Codominant

Answer: (B)

Dominance is the idea being tested. In a pair of alleles, one can mask the effect of the other in the phenotype. If an organism carries at least one copy of the dominant allele, that trait is expressed even if the other allele is recessive. The allele that does the masking is called the dominant allele. A familiar way to see this is the tall vs short plant: tall (dominant) traits appear in plants with TT or Tt, while only tt shows the short trait. The other options don’t fit this idea: a haploid cell is about chromosome sets, not allele interactions; a recessive allele is the one that can be masked; codominant refers to both alleles being shown together, not masking.