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Transcription is the process of copying a segment of DNA into RNA. Some segments of DNA are transcribed into RNA molecules that can encode proteins, called messenger RNA (mRNA). Other segments of DNA are transcribed into RNA molecules called non-coding RNAs (ncRNAs). Both DNA and RNA are nucleic acids, which use base pairs of nucleotides as a ...
RNA-dependent DNA polymerases are a specialized class of polymerases that copy the sequence of an RNA strand into DNA. They include reverse transcriptase , which is a viral enzyme involved in the infection of cells by retroviruses , and telomerase , which is required for the replication of telomeres.
Double stranded DNA that enters from the front of the enzyme is unzipped to avail the template strand for RNA synthesis. For every DNA base pair separated by the advancing polymerase, one hybrid RNA:DNA base pair is immediately formed. DNA strands and nascent RNA chain exit from separate channels; the two DNA strands reunite at the trailing end ...
While the sugar-phosphate "backbone" of DNA contains deoxyribose, RNA contains ribose instead. [6] Ribose has a hydroxyl group attached to the pentose ring in the 2' position, whereas deoxyribose does not. The hydroxyl groups in the ribose backbone make RNA more chemically labile than DNA by lowering the activation energy of hydrolysis.
An open reading frame (ORF) is a reading frame that has the potential to be transcribed into RNA and translated into protein. It requires a continuous sequence of DNA which may include a start codon, through a subsequent region which has a length that is a multiple of 3 nucleotides, to a stop codon in the same reading frame.
[1] [2] [3] During gene expression (the synthesis of RNA or protein from a gene), DNA is first copied into RNA. RNA can be directly functional or be the intermediate template for the synthesis of a protein. The transmission of genes to an organism's offspring, is the basis of the inheritance of phenotypic traits from one generation to the next.
Many viruses replicate this way. The enzymes that copy RNA to new RNA, called RNA-dependent RNA polymerases, are also found in many eukaryotes where they are involved in RNA silencing. [11] RNA editing, in which an RNA sequence is altered by a complex of proteins and a "guide RNA", could also be seen as an RNA-to-RNA transfer.
[2] Both types of pentoses in DNA and RNA are in their β-furanose (closed five-membered ring) form and they define the identity of a nucleic acid. DNA is defined by containing 2'-deoxy-ribose nucleic acid while RNA is defined by containing ribose nucleic acid. [1] In some occasions, DNA and RNA may contain some minor bases.