Which term describes a discrete unit of hereditary information located on DNA or RNA?

• A. Gene
• B. Allele
• C. Locus
• D. Chromosome

Answer: (A)

A gene is the discrete unit of hereditary information. It is a defined stretch of nucleic acid that carries the instructions to produce a functional product, usually a protein or a molecule of RNA. Genes are located at specific positions on a DNA molecule (a locus), and this organization underlies inheritance because different versions of a gene, called alleles, can segregate and assort in offspring. In contrast, a chromosome is the larger structure that contains many genes; an allele is a variant form of a gene; a locus is simply the gene’s position on the chromosome. So the term that best fits the description of a discrete hereditary unit located on DNA or RNA is gene.