Читать книгу Algorithms in Bioinformatics - Paul A. Gagniuc - Страница 17

Eukaryotes and prokaryotes prefer different strategies for synthesizing multiple proteins from a single DNA region (a transcription unit). In prokaryotes, several protein-coding areas (genes) are arranged linearly in a region called an operon, which is usually regulated by a single promoter. An operon is a cluster of coregulated genes with related functions [40]. Thus, operon expression leads to a number of proteins equal to the number of coding areas (genes) in the operon. All the genes in the operon are transcribed into a continuous RNA molecule, which is almost simultaneously translated into proteins. However, functional gene clustering (operon-like) has been reported in eukaryotes (i.e. fungi, plants, and animals) [40]. Eukaryotes, on the other hand, primarily use a single coding area interrupted by noncoding areas (introns). Different combinations between smaller fragments (exons) of the coding area lead to several types of RNAs and consequently to several types of proteins. The protein versions that originate from to a single gene are called “protein isoforms.” Note that protein isoforms are not necessarily functionally related [41].