Genes are units of inheritance. A gene is a segment of DNA that provides instructions for synthesis of a specific protein or a particular type of RNA. It may be defined as a segment of DNA which is responsible for responsible for inheritance and expression of a particular character.
Seymour Benzer (1955), introduced the terms, cistron, muton
and recon.
Cistron : (Unit of function) It is responsible for
expression of a trait. It is a segment of DNA having information for synthesis
of a particular protein or RNA. It can be several hundred bp (base pairs) long.
Muton : (Unit of mutation). It consists of a
few nucleotides, (one to few bp long). It is segment of DNA that can undergo
mutation.
Recon : (Unit of recombination). It is segment
of DNA that participates in recombination through crossing over during meiosis.
It consists of few to many base pairs.