Deoxyribonucleic acid (DNA) is a nucleic acid that contains the
genetic instructions used in the development and functioning of all known living
organisms with the exception of some viruses. The main role of DNA molecules is
the long-term storage of information.
Ribonucleic acid (RNA)
is a biologically important type of molecule that consists of a long chain of
nucleotide units. Each nucleotide consists of a nitrogenous base, a ribose
sugar, and a phosphate. RNA is very similar to DNA, but differs in a few
important structural details: in the cell, RNA is usually single-stranded, while
DNA is usually double-stranded; RNA nucleotides contain ribose while DNA
contains deoxyribose (a type of ribose that lacks one oxygen atom); and RNA has
the base uracil rather than thymine that is present in DNA. RNA is transcribed
from DNA by enzymes called RNA polymerases and is generally further processed by
other enzymes. RNA is central to protein synthesis. Here, a type of RNA called
messenger RNA carries information from DNA to structures called ribosomes. These
ribosomes are made from proteins and ribosomal RNAs, which come together to form
a molecular machine that can read messenger RNAs and translate the information
they carry into proteins. There are many RNAs with other roles – in particular
regulating which genes are expressed, but also as the genomes of most viruses.
A hairpin loop from a pre-mRNA.
Highlighted are the bases (light green) and backbone (sky blue).
RNA and DNA are
both nucleic acids, but differ in three main ways. First, unlike DNA which is
double-stranded, RNA is a single-stranded molecule in most of its biological
roles and has a much shorter chain of nucleotides. Second, while DNA contains
deoxyribose, RNA contains ribose (there is no hydroxyl group attached to the
pentose ring in the 2' position in DNA). These hydroxyl groups make RNA less
stable than DNA because it is more prone to hydrolysis. Third, the complementary
base to adenine is not thymine, as it is in DNA, but rather uracil, which is an
unmethylated form of thymine.
Like DNA, most biologically active RNAs, including mRNA, tRNA, rRNA, snRNAs and
other non-coding RNAs, contain self-complementary sequences that allow parts of
the RNA to fold and pair with itself to form double helices. Structural analysis
of these RNAs has revealed that they are highly structured. Unlike DNA, their
structures do not consist of long double helices but rather collections of short
helices packed together into structures akin to proteins. In this fashion, RNAs
can achieve chemical catalysis, like enzymes. For instance, determination of the
structure of the ribosome—an enzyme that catalyzes peptide bond
formation—revealed that its active site is composed entirely of RNA.
This site and its contents are not affiliated, connected,
associated with or authorized by the individual, family,
friends, or trademarked entities utilizing any part or
the subject's entire name. Any official or affiliated
sites that are related to this subject will be hyper
linked below upon submission
and Evisum, Inc. review.
Please join us in our mission to incorporate America's Four United Republics discovery-based curriculum into the classroom of every primary and secondary school in the United States of America by July 2, 2026, the nation’s 250th birthday. , the United States of America: We The
People. Click Here