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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.
RNA is susceptible to this base-catalyzed hydrolysis because the ribose sugar in RNA has a hydroxyl group at the 2’ position. [1] This feature makes RNA chemically unstable compared to DNA, which does not have this 2’ -OH group and thus is not susceptible to base-catalyzed hydrolysis. [1] Mechanism of base catalyzed RNA hydrolysis.
A parts washer heats water and the detergent in a closed cabinet and then sprays the heated sodium hydroxide and hot water at pressure against dirty parts for degreasing applications. Sodium hydroxide used in this manner replaced many solvent-based systems in the early 1990s [ citation needed ] when trichloroethane was outlawed by the Montreal ...
The double helix is the dominant tertiary structure for biological DNA, and is also a possible structure for RNA. Three DNA conformations are believed to be found in nature, A-DNA, B-DNA, and Z-DNA. The "B" form described by James D. Watson and Francis Crick is believed to predominate in cells. [2]
The chemical structure of DNA base-pairs . A base pair (bp) is a fundamental unit of double-stranded nucleic acids consisting of two nucleobases bound to each other by hydrogen bonds. They form the building blocks of the DNA double helix and contribute to the folded structure of both DNA and RNA.
Nucleic acids consist of a chain of linked units called nucleotides. Each nucleotide consists of three subunits: a phosphate group and a sugar (ribose in the case of RNA, deoxyribose in DNA) make up the backbone of the nucleic acid strand, and attached to the sugar is one of a set of nucleobases.
RNA adopts this double helical form, and RNA-DNA duplexes are mostly A-form, but B-form RNA-DNA duplexes have been observed. [14] In localized single strand dinucleotide contexts, RNA can also adopt the B-form without pairing to DNA. [15] A-DNA has a deep, narrow major groove which does not make it easily accessible to proteins.
For example, the RNA component of the human telomerase contains a pseudoknot that is critical for its activity. [7] The hepatitis delta virus ribozyme is a well known example of a catalytic RNA with a pseudoknot in its active site. [10] [11] Though DNA can also form pseudoknots, they are generally not present in standard physiological conditions.