RNA

RNA at one time could have been a likely carrier of genetic material and potentially performed the roles that proteins perform these days of catalysis. This is called the RNA hypothesis. But over evolution it has evolved to perform a wide variety of functions.

1. RNA is very important in protein synthesis
2. There are certain types of RNA that are catalytic (they are able to catalyze reactions like enzymes)

RNA is found in all aspect of protein synthesis. RNA carries the genetic information from DNA to protein by mRNA. It serves using its catalytic power in the protein machinery (rRNA). It is involved in linking amino acids to the appropriate sequence of DNA (genetic code) tRNA.

In protein synthesis that are three main types of RNA:

A. mRNA

• Sequence information to encode each protein is carried by mRNA. In eukaryotes, mRNA is produced by transcription in the nucleus and is transported to the cytoplasm where it is translated into protein. In prokaryotes, transcription and translation are not spatially separated and can occur simultaneously (co-transcriptional translation).
• mRNA is single-stranded in the sense that only one strand of the double-stranded DNA is present in the mRNA. However, mRNA, like other RNAs tends to be highly structured. Its structure is composed of short double-stranded regions between adjacent regions (called RNA hairpins (see picture above)) and longer-range contacts.

2. tRNA

• 75 nucleotide sequence, and is unique for each amino acid
• The 3-D structure of tRNA is needed for interaction with different species. It must interact with the enzyme that adds the appropriate amino acid to the appropriate tRNA it must then bind to the ribosome to transfer the amino acid to the polypeptide chain.

3. rRNA

• Is made up mostly RNA (3 separate RNA chains and about 50 proteins). It was shown that the RNA served more than a structure role but rather RNA was the catalyst inovled in protein synthesis. This helped establish the idea of the catalytic power of RNA, more and more different example of catalytic RNA has been investigated and discovered since then.