When an extra base is inserted into the DNA
sequence of a gene, the
protein doesn't work.
Which explains why?

small, big, or no change could occur in the phenotype. it could cause something as simple as a cats ears to curl backwards or something as frighting as death. it could also occur in the protien-coding area and have an effect on that but no effect on the amino acids. what has to occur is a changing in the hox gene or the control gene.

the endomembrane system i think