The equivalent of a structural gene is:

Cistron is a segment of DNA coding for a polypeptide. Eukaryotic structural gene is monocistronic whereas prokaryotic structural gene is polycistronic.

Replicon: Unit of DNA that undergoes replication. Muton: Unit of DNA which undergoes mutation. Recon: Unit of DNA which undergoes recombination. Operon is a co-ordinate group of genes such as structural gene, operator gene, promoter gene, regulator gene which function together and regulate a metabolic pathway as a unit, e.g., lac operon, trp operon, ara operon, his operon, val operon etc.