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Nucleosides are glycosylamines that can be thought of as nucleotides without a phosphate group. A nucleoside consists simply of a nucleobase (also termed a nitrogenous base) and a five-carbon sugar ( ribose or 2'-deoxyribose) whereas a nucleotide is composed of a nucleobase, a five-carbon sugar, and one or more phosphate groups.
This nucleotide contains the five-carbon sugar deoxyribose (at center), a nucleobase called adenine (upper right), and one phosphate group (left). The deoxyribose sugar joined only to the nitrogenous base forms a Deoxyribonucleoside called deoxyadenosine, whereas the whole structure along with the phosphate group is a nucleotide, a constituent of DNA with the name deoxyadenosine monophosphate.
Nucleosides are glycosylamines made by attaching a nucleobase to a ribose ring. Examples of these include cytidine , uridine , adenosine , guanosine , thymidine and inosine . Subcategories
The code is read by copying stretches of DNA into the related nucleic acid RNA in a process called transcription. Within cells, DNA is organized into long sequences called chromosomes. During cell division these chromosomes are duplicated in the process of DNA replication, providing each cell its own complete set of chromosomes.
DNA and RNA also contain other (non-primary) bases that have been modified after the nucleic acid chain has been formed. In DNA, the most common modified base is 5-methylcytosine (m 5 C). In RNA, there are many modified bases, including those contained in the nucleosides pseudouridine (Ψ), dihydrouridine (D), inosine (I), and 7-methylguanosine ...
Double-stranded RNA forms an A-type helical structure, unlike the common B-type conformation taken by double-stranded DNA molecules. The secondary structure of RNA consists of a single polynucleotide. Base pairing in RNA occurs when RNA folds between complementarity regions. Both single- and double-stranded regions are often found in RNA molecules.
In 1990, it was found in Petunia that introduced genes can silence similar genes of the plant's own, now known to be a result of RNA interference. [80] [81] At about the same time, 22 nt long RNAs, now called microRNAs, were found to have a role in the development of C. elegans. [82]
Nucleotides are nucleosides with a variable number of phosphate groups connected to the 5' carbon. Nucleoside triphosphates are a specific type of nucleotide. This figure also shows the five common nitrogenous bases found in DNA and RNA on the right.