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DNA exists as a double-stranded structure, with both strands coiled together to form the characteristic double helix. Each single strand of DNA is a chain of four types of nucleotides. Nucleotides in DNA contain a deoxyribose sugar, a phosphate, and a nucleobase.
Class 7: Double-stranded DNA viruses that replicate through a single-stranded RNA intermediate [ edit ] This small group of viruses, exemplified by the Hepatitis B virus, have a double-stranded, gapped genome that is subsequently filled in to form a covalently closed circle ( cccDNA ) that serves as a template for production of viral mRNAs and ...
It is similar to DNA but with the replacement of thymine by uracil and the adding of one oxygen atom. [1] Despite the structural similarities, much less is known about dsRNA. [2] They form the genetic material of some viruses (double-stranded RNA viruses). dsRNA, such as viral RNA or siRNA, can trigger RNA interference in eukaryotes, as well as ...
Retroviruses (Group VI) have a single-stranded RNA genome but, in general, are not considered RNA viruses because they use DNA intermediates to replicate. Reverse transcriptase , a viral enzyme that comes from the virus itself after it is uncoated, converts the viral RNA into a complementary strand of DNA, which is copied to produce a double ...
Unlike double-stranded DNA, RNA is usually a single-stranded molecule (ssRNA) [4] in many of its biological roles and consists of much shorter chains of nucleotides. [5] However, double-stranded RNA (dsRNA) can form and (moreover) a single RNA molecule can, by complementary base pairing, form intrastrand double helixes, as in tRNA.
The use of an RNase H activity during retroviral replication displays a unique strategy to copy a single-stranded RNA genome into a double-stranded DNA, since the minus-strand DNA are complementary and make base pairing to retrovirus genome in the first cycle of DNA synthesis. [16]
Directionality, in molecular biology and biochemistry, is the end-to-end chemical orientation of a single strand of nucleic acid. In a single strand of DNA or RNA, the chemical convention of naming carbon atoms in the nucleotide pentose-sugar-ring means that there will be a 5′ end (usually pronounced "five-prime end"), which frequently ...
Exposed single-stranded DNA can come under attack by endogenous mutagens, including DNA-modifying enzymes such as activation-induced cytidine deaminase, and can block replication forks to induce fork collapse and subsequent double-strand breaks. [24] As well, R-loops may induce unscheduled replication by acting as a primer. [12] [22]