Define Recon, Muton and Cistron

The terms Recon, Muton and Cistron were introduced by Seymour Benzer during the 1950s to study the detailed structure and function of genes at the molecular level. He worked on the rII region of T4 bacteriophage and used bacteriophage genetics to analyze how small changes in DNA affect phenotypes. At that time, the gene was considered as a single indivisible unit. But Benzer showed that a gene has a finer internal structure and can be divided into smaller functional units. Based on this, he proposed three molecular units: Recon, Muton and Cistron, each having a specific role related to recombination, mutation and expression.

Recon

Recon is defined as the smallest unit of recombination. It refers to the smallest segment of DNA within which crossing over cannot occur, but recombination can occur between two such units. According to modern molecular understanding, recombination between two genes or within a gene occurs at the level of nucleotides. So, a recon is considered as a single nucleotide pair, because it is the smallest unit between which recombination is possible. Recombination is a physical exchange of genetic material and it cannot happen within one nucleotide base. So, the recon helps in defining how fine or small recombination events can be at the molecular level.

Muton

Muton is the smallest unit of mutation. It is defined as the smallest portion of the genetic material where a change (mutation) can take place and be detected. Mutation means any alteration in the DNA sequence that brings a visible or detectable change in phenotype or protein function. In molecular terms, a muton is also equal to a single nucleotide pair, because even a change in one base can lead to a change in amino acid or gene function. Muton helps us to understand how small a mutation can be to affect gene function.

Cistron

Cistron is the functional unit of a gene. It is defined as the smallest stretch of DNA that codes for a complete polypeptide or functional RNA. It is basically the same as a gene in modern usage. The term cistron was derived from the "cis-trans test", which is a type of complementation test done to find out whether two mutations are present in the same gene or in two different genes. If two mutations fail to complement each other when present in trans, they are in the same gene or cistron. If they do complement, they are in different cistrons. Thus, the cistron refers to that entire region of DNA which contains all the necessary information to produce a functional product like a protein or RNA.







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