Eukaryote gene structure

The gene structure and the gene expression mechanism in eukaryotes are far more complicated than in prokaryotes. In typical eukaryotes, the region of the DNA coding for a protein is usually not continuous. This region is composed of alternating stretches of exons and introns. During transcription, both exons and introns are transcribed onto the RNA, in their linear order. Thereafter, a process called splicing takes place, in which the intron sequences are excised and discarded from the RNA sequence. The remaining RNA segments, the ones corresponding to the exons, are ligated to form the mature RNA strand. A typical multi-exon gene has the following structure (as illustrated in Figure ). It starts with the promoter region, which is followed by a transcribed but non-coding region called 5' untranslated region (5' UTR). Then follows the initial exon which contains the start codon. Following the initial exon, there is an alternating series of introns and internal exons, followed by the terminating exon, which contains the stop codon. It is followed by another non-coding region called the 3' UTR. Ending the eukaryotic gene, there is a polyadenylation (polyA) signal: the nucleotide Adenine repeating several times. The exon-intron boundaries (i.e., the splice sites) are signaled by specific short (2bp long) sequences. The 5'(3') end of an intron (exon) is called the donor site, and the 3'(5') end of an intron (exon) is called the acceptor site.

  

Figure: Typical eukaryote gene structure [].