The key differences between plasmid DNA and chormosomal DNA are as follows:

• The plasmid DNA is a circular, double-stranded extrachromosomal DNA, which is relatively smaller in size compared to chromosomal DNA.
• The presence of plasmid DNA is in prokaryotes only, whereas chromosomal DNA is present both in prokaryotes and eukaryotes. The eukaryotic genome contains a few to many linear chromosomes, while only one circular double-stranded chromosome is present in prokaryotes. The plasmid DNA vary in number, ranging from 1 to a thousand.
• The plasmid DNA contains the origin of replication and therefore it is self-replicative, naturally, while chromosomal DNA replicates with the genome.
• The chromosomal DNA is vital for proper cell functioning and reproduction, but plasmid DNA is not essential.
• The chromosomal DNA is transferred during the cell division, but the plasmid DNA is transferred by horizontal gene transfer.
• With the help of chromosomal DNA, genetic information on each organism is studied. The recombinant DNA technology is driven by plasmid DNA, as a new gene could be inserted in it and transcription of the inserted gene is possible since plasmid DNA contains the origin of replication.