A pair of genes which controls a trait is described as

Analyze the question: It asks for the term used for a pair of genes that control the same trait (for example, tall and short for height).

Explain the concept:

• Genes exist in alternative forms called alleles. They occupy the same position (locus) on homologous chromosomes and control the same characteristic.
• An organism inherits one allele from each parent, so each trait is controlled by a pair of alleles.

Check each option:

• A. Allele: the pair or alternative forms of a gene controlling a trait. This fits.
• B. Dominant: describes an allele that shows its effect even when only one copy is present. It is not the name for the pair.
• C. Hybrid: describes an organism with two different alleles (heterozygous). It describes the individual, not the gene pair.
• D. Recessive: describes an allele that is masked in the presence of a dominant one.
• E. Variant: a general word for a difference. It is not the standard genetics term for a gene pair.

Answer: The pair of genes controlling a trait is described as alleles, so the answer is A.

Tip: Remember "Allele = Alternative form of a gene." Dominant and recessive describe how alleles behave, while homozygous and heterozygous describe the combination of alleles in an individual.