genes

Genes are the basic units of heredity in living organisms. A gene is a specific sequence of nucleotides in DNA (or RNA in some viruses) that contains the information to produce a functional product, usually a protein or a molecule of RNA that has a cellular function. Genes are located on chromosomes and are transmitted from parents to offspring, forming the basis of heredity. Many organisms have tens of thousands of genes, with complexity increasing in higher organisms.

Most genes are transcribed into messenger RNA, which is translated into proteins, though some genes encode functional RNA molecules such as ribosomal RNA or transfer RNA. In eukaryotes, genes typically have regulatory regions (promoters, enhancers) and are split into exons and introns. Gene expression is controlled by a network of transcription factors, epigenetic modifications, and environmental signals, leading to tissue-specific and developmental-stage-specific patterns. Genetic variants, including mutations and polymorphisms, can alter gene function or regulation, contributing to diversity and disease. A large portion of genomes consists of noncoding DNA, including regulatory elements and pseudogenes.

Genetic inheritance follows patterns described by Mendel in classical genetics, with alleles of a gene determining variations in traits. Modern genetics integrates molecular biology, genomics, and bioinformatics, enabling mapping, sequencing, and comparative studies. Technologies such as gene editing and gene therapy aim to modify or correct genes to treat disease. Understanding genes and their regulation is central to fields ranging from medicine to agriculture, and ongoing research continues to reveal the complex networks that govern how genes shape biology.