"One gene-one protein" hypothesis states that one gene codes for one protein while the "one gene-one polypeptide" hypothesis states that one gene codes for one polypeptide chain of a protein having more than one type of polypeptide chains.
Explanation:
Beadle and Tatum proposed the one gene-one protein concept to explain the one-to-one correspondence between genes and proteins. Accordingly, one gene carries information to encode one protein. Since enzymes are proteins with catalytic power, a gene encodes the information to produce a single enzyme.
The "one gene-one protein" concept was later modified into the "one gene-one polypeptide" hypothesis. According to the "one gene-one polypeptide" hypothesis, one protein may have more than one polypeptide chain. One gene carries the genetic information to encode one polypeptide. Therefore, a protein with more than one type of polypeptide chains will be encoded by more than one gene.
