Hi,

Linearise the recombinant plasmid with a restriction enzyme which has a single site at the MCS. Before the enzyme digestion, please do confirm the same site is not present in the insert DNA sequence. Using agarose GE, compare the linear plasmid size with that of the native plasmid, the difference in sizes will be the approximate size of your gene.

Hope this will help you.

The restriction enzyme sites can be selected based on the restriction enzyme maps generated for gene sequence using NEB cutter online tool and Bio-edit. These enzyme sites should absent within the gene of interest and also should compatible with cloning vector and expression vector.

Most people use restriction enzymes as a first screen to check a plasmid. Choose restriction enzymes that are present in the insert as well the vector. Also, choose enzymes that flank the insert without cutting inside it. The first restriction digest confirms that there is indeed an insert in your plasmid and can also determine the orientation of the insert (see below). The second digest confirms the size of the insert. you can find details in the link below. Hope this will help you.

https://bitesizebio.com/25049/three-important-things-to-check-after-obtaining-your-plasmid/