A Level Biology Practice Exam

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What is a gene?

A type of RNA molecule
A structure made up of ribosomes
A section of DNA coding for a protein
A type of lipid involved in cell membranes

The correct answer is: A section of DNA coding for a protein

A gene is best defined as a section of DNA that contains the instructions for synthesizing proteins, which are essential for various functions and structures within an organism. This segment of DNA is organized in a specific sequence of nucleotides, which encode the amino acid sequences of proteins. The functionality of a gene lies in its ability to govern the production of proteins, thus playing a critical role in an organism's phenotypic expression and biological processes. In this context, the other options do not accurately represent what a gene is. RNA molecules play a significant role in the transcription and translation processes but are not classified as genes themselves. Ribosomes are cellular structures composed of RNA and proteins that are involved in protein synthesis but do not constitute genes. Lipids are organic molecules that form cell membranes and have diverse functions in the body, but they are not related to the genetic coding or functioning of genes.