is present in several forms - messenger RNA (mRNA), transfer
RNA (tRNA), and ribosomal RNA (rRNA). Each of these RNA
forms is involved in different steps of protein synthesis.
mRNA is generated from DNA and is the template for protein
synthesis. tRNA is critical to the translation of the mRNA
sequence into protein sequence. rRNA are components of the
ribosomes which are the sites of protein synthesis.
RNA is a polymer that contains ribose
rather than deoxyribose sugars. The normal base composition
is adenine, uracil, guanine, and cytosine.
RNA can form double
stranded duplexes. These duplexes are in the A conformation
because the 2'OH
precludes the B conformation.
More commonly, RNA is single stranded
and can form complex and unusual shapes. One example is
contains about 70 bases that are folded such that there
are base paired stems and open loops. The overall shape
of the completely folded tRNA is L shaped.
Another very interesting type of RNA
is called a ribozyme, which is an RNA that has catalytic
structures have been characterized.
Ribosomal subunits have been studied
in great detail [Gallery]
ribosomal subunit and 50S
ribosomal subunit consists of rRNA and multiple proteins.