Geneexpression

Gene expression is the process by which information encoded in a gene is used to produce a functional product, typically a protein or a molecule of RNA. In most organisms, gene expression begins with transcription, where RNA polymerase reads a gene's DNA sequence to synthesize messenger RNA (mRNA). In eukaryotes, mRNA is processed and exported to the cytoplasm, where translation on ribosomes produces a polypeptide. Some genes encode noncoding RNAs that play regulatory or structural roles.

Expression is tightly regulated at multiple levels. DNA sequences such as promoters and enhancers recruit transcription factors and the transcriptional machinery. Epigenetic mechanisms, including DNA methylation and histone modifications, alter chromatin structure to enable or restrict access to genes. Post-transcriptional regulation controls mRNA splicing, editing, transport, stability, and translation efficiency. Post-translational regulation of proteins further modulates activity and lifespan.

Context matters: gene expression varies between cell types, developmental stages, and in response to environmental cues. Single genes can have tissue-specific expression, while networks of genes coordinate complex processes such as development, immune responses, and metabolism. Dysregulation of gene expression is implicated in many diseases, including cancer, neurological disorders, and metabolic syndromes.

Studying gene expression involves techniques such as RNA sequencing, microarrays, quantitative PCR, and in situ hybridization. More recently, single-cell RNA sequencing provides expression profiles at the level of individual cells, revealing cellular heterogeneity and dynamic responses.

Understanding gene expression informs fields from basic biology to medicine and biotechnology, including diagnostics, pharmacogenomics, and synthetic biology.