Answer:
one gene, one polypeptide hypothesis
Step-by-step explanation:
A protein may have one or more than one polypeptide chain. Each of the different types of the polypeptide chain of a protein is encoded by a specific gene. Earlier it was thought that one gene codes for one enzyme and it was called one gene-one enzyme hypothesis.
However, it soon became evident that some proteins are heterogeneous in nature which means that they have more than one type of polypeptide chains which in turn are encoded by different genes. For instance, the insulin hormone has two types of polypeptide chain namely A and B chains. They are encoded by different genes.