What is a gene?

A gene is fundamentally defined as a segment of DNA that contains the instructions necessary for synthesizing a specific protein. This definition highlights the role of genes as functional units of heredity that encode the information required to produce proteins, which are crucial for various biological functions and processes within an organism.

Proteins are made up of amino acids, and their specific sequences are determined by the genetic code contained within the corresponding gene. When a gene is expressed, the information is transcribed into messenger RNA (mRNA), which is then translated into a protein. This process underscores the vital connection between genes and protein synthesis, illustrating how genetic information is utilized in cellular functioning.

Other options do touch on related concepts, such as the role of genes in heredity and their potential non-coding segments, but defining a gene primarily as a segment of DNA responsible for producing a specific protein accurately reflects its biological role and importance within the context of genetics and molecular biology.