Gene
A gene is a stretch of genetic sequence that helps produce a functional product, usually a protein or a functional RNA molecule. Genes are carried in genomes, inherited through reproduction, regulated by cells, and changed by mutation and variation.
What a gene is
A gene is a sequence of genetic material that carries information for making a functional product. Many genes encode proteins, while others encode RNA molecules that work without becoming proteins. The exact boundaries of a gene can be complex, but the core idea is that genes are functional units within a genome.
Genes inside genomes
Genes are parts of larger genomes. In eukaryotes such as humans, genes are located on chromosomes in the nucleus, with additional genes in mitochondrial DNA. Bacteria usually carry genes on a circular chromosome and sometimes on plasmids. Viruses may carry genes in DNA or RNA, depending on the virus.
DNA, RNA, and proteins
For a protein-coding gene, the cell usually copies DNA into messenger RNA through transcription. Ribosomes then read the RNA in three-letter codons and build a chain of amino acids that folds into a protein. RNA genes skip the protein step: their RNA product itself performs a job, such as helping build ribosomes or regulate other genes.
Gene structure
A gene is more than a single uninterrupted recipe. In many eukaryotic genes, coding exons are separated by introns that are removed from RNA after transcription. Nearby promoters and more distant regulatory regions help control when and where the gene is used, even if those control regions are not always counted as part of the gene itself.
Expression and regulation
Gene expression means using genetic information to make a functional RNA or protein product. Cells regulate expression so different cell types can use different genes from the same genome. A liver cell, nerve cell, and immune cell carry nearly the same DNA, but they activate different sets of genes to do different work.
Alleles and inheritance
Most people inherit two copies of many genes, one from each biological parent. Versions of a gene with small sequence differences are called alleles. Some alleles have no obvious effect, some change a visible trait, and some raise or lower the chance of particular health conditions.
Mutation and variation
A mutation is a change in genetic sequence. Mutations can replace one DNA base, add or remove bases, duplicate a gene, disrupt a regulatory region, or rearrange larger chromosome segments. Their effects range from neutral to harmful to useful, depending on the gene, the cell, and the environment.
Genes and traits
A single gene can strongly influence a trait, but many traits are shaped by many genes working with environment, development, and chance. Height, immune response, metabolism, and disease risk often involve networks of genes rather than one simple switch. This is why identifying a gene is only the beginning of understanding a trait.
Why it matters
Genes connect molecular biology to inheritance, medicine, evolution, agriculture, and biotechnology. Understanding genes helps scientists study disease, trace ancestry, improve crops, monitor pathogens, design genetic tests, and develop tools such as gene therapy and genome editing.