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Gene structure is the organisation of specialised sequence elements within a gene.Genes contain most of the information necessary for living cells to survive and reproduce. [1] [2] In most organisms, genes are made of DNA, where the particular DNA sequence determines the function of the gene.
Eukaryotic Transcription. Eukaryotic transcription is the elaborate process that eukaryotic cells use to copy genetic information stored in DNA into units of transportable complementary RNA replica. [1] Gene transcription occurs in both eukaryotic and prokaryotic cells. Unlike prokaryotic RNA polymerase that initiates the transcription of all ...
Early speculations on the size of a typical gene were based on high-resolution genetic mapping and on the size of proteins and RNA molecules. A length of 1500 base pairs seemed reasonable at the time (1965). [14] This was based on the idea that the gene was the DNA that was directly responsible for production of the functional product.
Because these transcripts can be potentially translated into different proteins, splicing extends the complexity of eukaryotic gene expression and the size of a species proteome. [13] Extensive RNA processing may be an evolutionary advantage made possible by the nucleus of eukaryotes.
Gene promoters are typically located upstream of the gene and can have regulatory elements several kilobases away from the transcriptional start site (enhancers). In eukaryotes, the transcriptional complex can cause the DNA to bend back on itself, which allows for placement of regulatory sequences far from the actual site of transcription.
Regions of the genome with protein-coding genes include several elements: Enhancer regions (normally up to a few thousand basepairs upstream of transcription).; Promoter regions (normally less than a couple of hundred basepairs upstream of transcription) include elements such as the TATA and CAAT boxes, GC elements, and an initiator.
Unlike prokaryotes where exon-intron organization of protein coding genes exists but is rather exceptional, eukaryotes generally have these features in their genes and their genomes contain variable amounts of repetitive DNA. In mammals and plants, the majority of the genome is composed of repetitive DNA. [38]
Saccharomyces cerevisiae was the first eukaryotic organism to have its complete genome sequence determined.. This list of "sequenced" eukaryotic genomes contains all the eukaryotes known to have publicly available complete nuclear and organelle genome sequences that have been sequenced, assembled, annotated and published; draft genomes are not included, nor are organelle-only sequences.