intronrich

Intronrich is a nonstandard term used in genomics to describe genes or genomes with a high density of introns—noncoding sequences within genes that are interrupted by exons and subsequently removed during RNA processing. It is not a formal classification.

The concept is used to discuss genome architecture across eukaryotes, where some lineages show many introns per gene or large total intronic DNA relative to coding sequences. Intron-rich genes display extensive alternative splicing and complex regulatory potential.

Characteristics: high intron density (introns per gene), variable intron length with often long introns, large fraction of noncoding DNA within genes, enriched regulatory elements within introns, and elevated transcriptome complexity due to splicing options.

Evolution and implications: intron gain and loss shape intron-richness; intron-richness may arise through intron proliferation or retention of ancestral introns; its evolutionary significance is debated and may reflect trade-offs between regulatory potential and transcriptional cost. Some studies link intron-rich loci to developmental regulation and tissue-specific expression.

Measurement and caveats: researchers quantify intron-richness using metrics such as intron density (introns per gene), mean intron length, and the proportion of a gene's sequence that is intronic. Accurate assessment depends on high-quality genome annotation and assembly; misannotations or incomplete genomes can bias results.

See also: intron, alternative splicing, gene architecture, intron evolution.