noncoding

Noncoding refers to genetic material or transcripts that do not code for proteins. Unlike protein-coding sequences, which are translated into amino acids, noncoding regions may be transcribed but not translated. In many genomes, coding sequences are only a fraction of the total, while noncoding DNA and noncoding RNA genes comprise the remainder.

Noncoding DNA includes introns within genes, intergenic regions, and regulatory elements such as promoters, enhancers, silencers, and insulators, as well as repetitive elements and transposons. Some noncoding DNA regulates gene expression or helps organize chromatin; other portions may be nonfunctional remnants. The boundary between functional and neutral noncoding DNA is an active area of research.

Noncoding RNA genes produce RNA molecules that perform functions without being translated. Classical examples include ribosomal RNA and transfer RNA, essential for protein synthesis, and small nuclear and small nucleolar RNAs involved in RNA processing. Regulatory noncoding RNAs include microRNAs, small interfering RNAs, Piwi-interacting RNAs, and long noncoding RNAs, which influence gene expression, chromatin state, and RNA metabolism.

Understanding noncoding elements has grown with genome sequencing. Mutations in regulatory regions or noncoding RNA genes can affect gene expression and contribute to disease. Research aims to map functional noncoding elements and reveal their roles in development, evolution, and health, improving annotation of genomes and informing approaches such as gene therapy and precision medicine.