Gene Expression
The process by which information in a gene produces a functional product: transcription of DNA to RNA and translation of RNA to protein.
Gene expression is the process by which the information stored in a gene is used to produce a functional product, usually a protein. The flow is summarized by the central dogma of molecular biology, formulated by Francis Crick in 1957: DNA is transcribed into RNA, and RNA is translated into protein. It is the pathway that turns the static genome — the same in nearly every cell of an organism — into the dynamic chemistry of a living body.
Transcription copies a gene from DNA into messenger RNA (mRNA). RNA polymerase binds a promoter upstream of the gene, unwinds the double helix, and synthesizes a complementary RNA strand, then stops at a terminator. In eukaryotes, the primary transcript is processed: introns are spliced out, a cap and a poly-A tail are added, and alternative splicing can produce different proteins from the same gene — a major source of proteome diversity. The mRNA then travels to the cytoplasm.
Translation reads the mRNA in triplets of nucleotides called codons, each coding for one amino acid. Ribosomes — molecular machines of RNA and protein — match each codon with a transfer RNA (tRNA) bearing the corresponding amino acid, and join the amino acids into a growing polypeptide chain. The genetic code is nearly universal: with 64 codons for 20 amino acids, most amino acids have several codons, and three stop codons end the chain. The resulting protein folds into its working shape, often assisted by chaperones.
Expression is tightly regulated: a typical human cell expresses only a fraction of its genes, and the pattern defines the cell's identity. Regulation happens at every level — chromatin structure, transcription factors binding promoters and enhancers, RNA stability, translation control, and protein degradation. Mutations in genes alter their products, and technologies such as CRISPR–Cas9 now allow genes to be edited directly. Understanding expression connects the classical genetics of Mendelian inheritance to molecular mechanism: a gene is a unit of heredity precisely because its expression produces an observable trait.
Tags
central dogma genetics transcription translation