A recessive allele shows its trait only in which condition?

• A. When the dominant allele is present
• B. When the dominant allele is not present
• C. In all genotypes
• D. Only in heterozygotes

Answer: (B)

Recessive traits appear only when there are two copies of the recessive allele, because a dominant allele masks the recessive one in any heterozygote. If a dominant allele is present, the dominant phenotype shows up, hiding the recessive trait. So the recessive trait is visible only when there is no dominant allele at all, meaning the organism has two recessive alleles. In other genotypes (one or two dominant alleles), you’ll see the dominant phenotype instead.