What is true about a recessive gene?

A recessive gene is characterized by the requirement of two copies, one from each parent, to manifest its trait in the organism's phenotype. This means that an individual must inherit the recessive allele from both parents for the associated trait to be expressed. If only one copy of the recessive gene is present, the dominant gene, if it exists, will mask the effect of the recessive gene, leading to the dominant trait being expressed instead.

This concept highlights the nature of allele interaction in diploid organisms, where pairs of alleles (one from each parent) determine traits. A single recessive allele is insufficient for the phenotype to reflect the recessive trait, emphasizing the need for two copies for expression. Understanding this is crucial for grasping basic principles of inheritance, such as those outlined in Mendel's laws of inheritance.

The other options either misrepresent the role of recessive genes or their characteristics in genetic inheritance.