What kind of genetic trait is expressed even when only one copy is present?

• A. Recessive
• B. Homozygous
• C. Dominant
• D. Heterozygous

Answer: (C)

The correct answer is based on the concept of dominant genetic traits. A dominant trait is one that is expressed in the phenotype when at least one copy of the dominant allele is present in an individual’s genotype. This means that if an individual has one dominant allele, the characteristic associated with that allele will manifest in their physical appearance, regardless of whether a second allele is present or whether it is recessive.

For instance, consider the trait for a specific flower color. If the allele for purple flowers is dominant and the allele for white flowers is recessive, an individual with just one purple flower allele (heterozygous) will still display purple flowers. This showcases the dominance of the allele—its ability to mask or override the effect of the recessive allele present.

In contrast, recessive traits require two copies of the recessive allele to be expressed. Homozygous refers to having two identical alleles for a trait, while heterozygous refers to having two different alleles. Hence, the dominance of certain traits hinges on the presence of just one allele in the genotype, highlighting the nature of how traits are inherited and expressed.