RNA world

All modern organisms have DNA as a store of genetic information, RNA as a message and proteins as their major cellular catalyst. This shows that the organism from which all cellular life began had these properties, which is called 'LUCA', meaning Last Universal Common Ancestor. This is a very complicated model and there are many questions surrounding the origin of life, for example, how did it all start? Where did DNA come from, as proteins are involved in its replication? DNA codes for proteins, so how can proteins have been produced first, as they are believed to have been? What came first - polynucleotides or polypeptides?

The RNA world is the currently accepted hypothesis which answers these questions. This is based around the idea that RNA, as a message, led to proteins (this stage can be refered to as the RNP world), which became catalysts. which led to DNA, the store of genetic information.

Evidence supporting the RNA world

RNA can behave as both a store of genetic information and as a cellular catalyst.

RNA is capable of replicating itself without the use of enzymes.

It is more likely that a single molecule was capable of replicating itself, rather than two different molecules being synthesised by random chemical reactions in the same place, at the same time.

Ribosomes use RNA to catalyse pepide bond formation of amino acids in DNA.

The RNA world could easily have evolved into our current day mechanism of storing genetic information, but it is unlikely that an efficient system of self-replicating molcules could have been added to with RNA.