In figure 6-19,
a) The square and triangular pegs in the first protein shows the binding site, where as the hole represent the binding site in the second protein. The two proteins normally fit together to provide certain type of cellular function. If any mutation causes change in the shape of any one protein, it can no longer fit with the other. As a result, the function of the protein will be lost. However, the suppressor mutation causes a compensatory change in the shape of the second protein. This change helps the two proteins to fit together and continue their role in the cellular activity.
b) No. Because of the fact that the suppressor mutation changes the shape of the second protein only, a mutation in the other gene is also required to make it phenotypically a wild type.