The Science of Existence (122-9) continued


Genes in prokaryotes are continuous DNA strands. In contrast, eukaryotic genes have coding regions (exons) interspersed with noncoding segments (introns).

Introns are nucleotide segments in either DNA or RNA, some of which may be self-splicing: able to extract and insert themselves into gene products. Some introns encode specific proteins; others, functional RNA.

Introns exist in the genomes of bacteria and eukaryotes. Their capabilities are not well understood, but they are known to enhance gene expression. Introns in yeast cells have been found to promote resistance to starvation and promote growth.

DNA coding regions typically comprise several separated exons (coding sequences) that are joined as an RNA transcript. Exons are formed from precursor RNA segments (introns) that are removed from a gene by RNA splicing.

Simultaneous encoding of amino acid and regulatory information within exons is a major functional feature of complex genomes. The information architecture of the received genetic code is optimized for superimposition of additional information, and this intrinsic flexibility has been extensively exploited in evolution. ~ American geneticist Andrew Stergachis et al

When proteins are made from intron-containing genes, RNA splicing is part of the RNA processing pathway that follows transcription and precedes translation.