Exons interruptions

Genes that are expressed usually have introns that interrupt the coding sequences. A typical eukaryotic gene, therefore, consists of a set of sequences that appear in mature mRNA (called exons) interrupted by introns. The regions between genes are likewise not expressed, but may help with chromatin assembly, contain promoters, and so forth. See Figure 12-6. 

The major path for extracting different information from the same pre-mRNA uses alternative splicing. The genetic information encoding a protein in higher eucaryotes is usually found in pieces of coding sequences, or exons, interrupted by non-coding sequences, the introns. For the formation of the mature mRNA, the introns must be... 

Another part of the picture in vertebrates and dowering plants is that genes are often not continuous segments of the DNA chain. Instead, a gene will begin in one small section of DNA called an exon, then be interrupted by a noncoding... 

The Coding Portions (Exons) of Most Eukaryotic Genes Are Interrupted by Introns... 

Many genes in eukaryotic cells, and a few in bacteria, are interrupted by noncoding sequences called introns. The coding segments separated by introns are called exons. 

To continue the thoughts that were interrupted by the comets as to why this unpredictability. Examining the nucleic acids from different places, similarity seemed extensive even between samples that came from widely separate spots. There are only four main components in addition to odd occasional nucleotides and that did not make for much variation, and the idea offered itself that life would eventually be read from any nucleic acid by cut and paste processes in line with energy minima. That might be the origin of exon/intron structures in eukaryotes.7... 

The precise function of introns is unknown. Nevertheless, there is some evidence that the exons, or coding sequences, give rise to structural domains in the final protein product. It is therefore considered that interrupted genes (the exons), as they are called, may reflect an evolutionary process in which combinations of various exons gave rise to different proteins through the joining of different protein domains. 

The initiation codon, usually an AUG, signals the start of translation, and a termination codon marks the end of the translated region. In the analysis of prokaryotic DNA sequences, the signals include the transcriptional and translational initiation sites, the ribosome-binding site, and the transcriptional and translational termination sites. Due to the interrupted nature of the eukaryotic genes, the signals include the translation initiation sites, the intron/exon boundaries (splice sites), translational termination sites, and the polyadenylation sites. 

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