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The resulting DNA can be merged with the DNA genome of the host cell. The main enzyme responsible for synthesis of DNA from an RNA template is called reverse transcriptase. [65] In the case of HIV, reverse transcriptase is responsible for synthesizing a complementary DNA strand (cDNA) to the viral RNA genome.
A eukaryotic cell has a nucleus that separates the processes of transcription and translation. Eukaryotic transcription occurs within the nucleus where DNA is packaged into nucleosomes and higher order chromatin structures. The complexity of the eukaryotic genome necessitates a great variety and complexity of gene expression control.
Promoters are located near the transcription start sites of genes, upstream on the DNA (towards the 5' region of the sense strand). Promoters can be about 100–1000 base pairs long, the sequence of which is highly dependent on the gene and product of transcription, type or class of RNA polymerase recruited to the site, and species of organism ...
In general gene expression is regulated through changes [44] in the number and type of interactions between molecules [45] that collectively influence transcription of DNA [46] and translation of RNA. [47] Some simple examples of where gene expression is important are: Control of insulin expression so it gives a signal for blood glucose regulation.
Cis-regulatory DNA sequences that are located in DNA regions distant from the promoters of genes can have very large effects on gene expression, with some genes undergoing up to 100-fold increased expression due to such a cis-regulatory sequence. [36] These cis-regulatory sequences include enhancers, silencers, insulators and tethering elements ...
Overview of eukaryotic messenger RNA (mRNA) translation Translation of mRNA and ribosomal protein synthesis Initiation and elongation stages of translation involving RNA nucleobases, the ribosome, transfer RNA, and amino acids The three phases of translation: (1) in initiation, the small ribosomal subunit binds to the RNA strand and the initiator tRNA–amino acid complex binds to the start ...
RecQ is a family of DNA helicase enzymes that are found in various organisms including bacteria, archaea, and eukaryotes (like humans). These enzymes play important roles in DNA metabolism during DNA replication, recombination, and repair. There are five known RecQ helicase proteins in humans: RecQ1, BLM, WRN, RecQ4, and RecQ5.
The magnesium ion (yellow) is located at the enzyme active site. The 17-bp transcriptional complex has an 8-bp DNA-RNA hybrid, that is, 8 base-pairs involve the RNA transcript bound to the DNA template strand. [17] As transcription progresses, ribonucleotides are added to the 3′ end of the RNA transcript and the RNAP complex moves along the DNA.