UNITS OF A GENE

After much extensive work done by the molecular biologists the nature of gene became clear. A gene can be defined as a poly nucleotide chain that consists of segments each controlling a particular trait. Now, genes are considered as a unit of function (cistron), a unit of recombination (recon) and a unit of mutation (muton).

Cistron: A single mRNA is transcribed by a single gene. Therefoer, one-gene-one mRNA hypothesis was put forth. Exceptionally, a single mRNA is also transcribed by more than one gene and it is said to be polycistronic. Therefore, the concept has been given as one-gene-one protien hypothesis. The protiens are the polypeptide chains of amino acids translated by mRNA. Therefore, it has been correctly used as one-gene-one polypeptide hypothesis.

Recon: I n a cistron the recombinational units may be more than one. Thus the smallest unit capable of undergoing recombination is called as recon.

Muton: It may be defined as '' the smallest unit of DNA which may be changed is the nucleotide''. Therefore, cistron is the largest unit in size followed by recon and muton. This can be explained that a gene consists of several cistron, a cistron contains many recons, and a recon a number of mutons. However if the size of a recon is equal to muton, there would be no possibility in recon for consisting of several mutons.