How could I introduce a novel variant in a gene sequence and assess its effect?

Question

[ritiksinha005]

I need to introduce a novel variant and assess its pathogenicity as a part of an academic exercise. As of now I am using reference exome sequences and introducing them manually. This is tedious and quite difficult to tell if it is novel. I am looking for a way preferably a web tool to test multiple sites.

[cpad0112]

write a script to either randomly replace or delete nucleotides in exome sequences. or use some thing like this: https://github.com/lh3/wgsim. Use google.