It should be realized that at a particular stage of research, the number of mutational sites will be minimum, due to experimental limitations of handling limited population. As experimental techniques are refined, better resolution is possible and the existing mutational sites are further resolved into more sites. As mentioned above, the smallest unit capable of undergoing recombination is called recon. A recon is further subdivisible into units of mutations called mutons, and several mutons in a recon will not be separable due to recombination. Since mutons in a recon can not be identified due to recombination test, they can be recognized through the changes in amino acid sequence of a polypeptide chain synthesized by, or through the nucleotide sequence of, the cistron in question. Since a mutation can take place by single base replacement, a single nucleotide pair is the ultimate limit of muton. Therefore, cistron, recon and muton are the units, in the descending order of size and since gene is not synonymous to cistron, as explained above, it will be at the top of this hierarchy. Thus a gene can consist of several cistrons, a cistron of several recons and a recon of several mutons. A recon and a muton may be of the same size, so that in such a case recon may not consist of several mutons.
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