gene

A gene is the basic unit of heredity. It is a specific sequence of nucleotides in DNA (or RNA in some viruses) that can influence a particular trait or process, typically by directing the synthesis of a gene product. Genes are located on chromosomes and are inherited from parents, with their expression contributing to development and function.

Most genes encode proteins, but many encode functional RNA molecules such as rRNA, tRNA, microRNA, or long noncoding RNA. A gene's coding region is transcribed into RNA, which is processed and, for protein-coding genes, translated into a protein; noncoding RNAs have roles as RNAs themselves.

Gene expression is regulated by promoters and other regulatory elements, transcription factors, epigenetic modifications, and noncoding RNAs. Expression patterns vary by tissue and developmental stage and can be influenced by environment, mutations, and chromatin structure.

Genetic variation in genes leads to different alleles that influence traits. Some follow Mendelian patterns, while many traits are polygenic and influenced by environment. Mutations can disrupt function and contribute to disease or, less commonly, beneficial variation.

The study of genes includes genetic mapping and sequencing, functional studies in model organisms, and large-scale analyses such as genome-wide association studies. Technologies such as gene editing and gene therapy aim to modify gene sequences or expression to treat disease.