RNA is the little known cousin of DNA. Standing for Ribonucleic Acid, RNA is mainly different from DNA in the sugar (ribose) that makes up its backbone. DNA is famous for being the code for life, but in fact it is a code for making proteins for our cells. For a long time, our understanding of RNA was limited to its role as a molecule that allowed the coding language of DNA to be translated into proteins. In the last couple of decades though, RNA has caused excitement throughout the scientific world when it was discovered that RNA was more than a mere translator.
Our understanding of RNA used to consist of three molecules -mRNA, tRNA, and rRNA. Broadly speaking, RNA can be thought of as a copy. If DNA is the blueprint that needs to be kept secure in the centre of the cell, RNA is the messenger that can take the information that DNA codes for out into the complex world of the cell where proteins are made. Proteins, and the enzymes they form, make life possible – from producing energy to removing waste; proteins are essential for cells to function.
RNA not only allows DNA to be kept safely, it also allows for many different proteins to be made from the same piece of DNA. A sequence of DNA is first copied into a single strand of mRNA. The mRNA sequence has many sections that can be cut out or rearranged (known as splicing), which makes it possible to produce different sequences, and therefore proteins all from the same original piece of DNA. This means that the cell can regulate which proteins are made according to the need for the protein at that time.
DNA and RNA are made of ‘bases’. Short strands of RNA (up to 21 bases) have recently been found to be capable of silencing genes. If the 21 bases of the short stranded (siRNA) match a DNA sequence, the siRNA effectively destroys the mRNA for that DNA sequence. This results in that gene being silenced as no protein can be made.
The role of RNA as gene silencer has revolutionized science. Gene silencing can be used to study the function of various genes by switching them off. This can help answer questions about genes and their roles in diseases. More importantly, its a potential way of treating genetic diseases and cancers where genes are misbehaving, although there’s still much more research required into this area.
Researchers have discovered that short stranded or micro-RNAs naturally occur in our cells, where they can regulate cellular development. This means that micro-RNA molecules switch off genes, and so direct a cell to become a particular type – a muscle cell, for example.
Clearly, RNA has many diverse roles to play – cellular interpreter, gene silencer and cell regulator. In time, RNA could even challenge the fame of its cousin DNA as the more dynamic and versatile molecule of the two.