Information encoded in the DNA molecule is passed on to the mRNA which are synthesized in the nucleus on DNA templates. It is a single-stranded molecule, much smaller than DNA and can easily pass through the nuclear membrane to the cytoplasm. The precursors to the cytoplasm. The precursors of mRNA make their appearance in heterogeneous nuclear RNA (hnRNA), a mixture of different types of RNA molecules. The heterogeneous RNA contains many transcripts that are discarded before the actual mRNA moves to the cytoplasm to participate in proteins synthesis.

The true nature of the messenger RNA was revealed by Jacob and Monod in 1961 while using bacterial DNA for the synthesis of enzyme protein β-mRNA is an intermediate molecule that survives only for a brief period but with  its concentration remaining constant at any point of time. It was, suggested that mRNA molecules are continually synthesized and their rate of destruction equals the rate of synthesis, hence this constancy. The half-life of procaryotic mRNA is few minutes, whereas that of the eucaryotes is about a few hours.



Once mRNA reaches the cytoplasm, it attaches itself to the ribosomes. This association depends upon the concentration (10^-2M) promotes attachment, while low concentration (10^-4) allows dissociation. One molecule of DNA can serve as a template for producing a large number of mRNA molecule, each of which may have identical genetic information.

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