Hi, Md. Maksudul, Yes you can, but it depends of the plasmid structure, You need to know the sequence of your plasmid to find an ORF that you can replace or inactivate with your insertion (. Be careful when chooses your plasmid, there is a lot of plasmids with specific selection markers available.
Hello, it is possible to add another gene to your plasmid as long as you know the full sequence of your plasmid, so you can determine the insertion site.