Over 2600 genetic diseases have been found where a change in a single gene is linked to the disease. One of the questions we might ask is how those mutations change the shape and possibly the function of a protein?
If the structures of the mutant and wild type (normal) proteins have been solved, NCBI has a program called VAST that can be used to align those structures. I have an example here where you can see how a single amino acid change makes influenza resistant to Tamiflu®.
This 4 minute movie below shows how we can obtain those aligned structures from VAST and view them with Cn3D.