Provide one sentence information about plasmid with respect to its

(a) Chemical nature

(b) Its duplication

(a) Plasmid is a small, circular, extra chromosomal genetic material which can replicate independently within a cell. It is a double stranded DNA molecule found mostly in bacterial cells and sometimes in eukaryotes. 

(b) Plasmid undergoes duplication by the process of rolling circle replication. 

This method of replication you will study in higher classes.