What is a gene?

• A. A basic unit of heredity—a sequence of DNA that codes for a functional product (protein or RNA).
• B. A lipid molecule that stores energy.
• C. A protein that speeds up chemical reactions.
• D. A cell organelle that stores genetic material.

Answer: (A)

A gene is a unit of heredity—a defined stretch of DNA that contains the instructions to produce a functional product, usually a protein or a molecule of RNA. In organisms, genes sit on chromosomes inside the cell nucleus, and the information they carry is read first by transcription to make an RNA copy, then translated to build proteins (or, in some cases, the RNA itself has a functional role). This is how genes influence traits and are inherited from one generation to the next. Some genes code for non-coding RNAs that have regulatory or structural roles as well. The other options mix up function: a lipid that stores energy is not genetic information; a protein that speeds up chemical reactions is an enzyme, a product of gene expression, not the gene itself; and an organelle that stores genetic material is a place where genes are found, not the gene.