Correct option (b) cistron Explanation Cistron is the segment of DNA which determines the synthesis of complete polypeptide. Thus, it is considered as equivalent to a structural gene. Therefore, option (b) is correct and others are incorrect. Concept Enhancer Eukaryotic structural gene ls monocistronic whereas prokaryotic structural gene is polycistronic. Muton Smallest unit of DNA in which mutation occurs. Operon Functional unit of genomic DNA containing a cluster of genes under control of single promoter. Recon Smallest unit of DNA for recombination.