A research group of geneticists found a fruit fly mutant that shakes vigorously when anaesthetized with ether. Their studies showed that the shaker mutant has K+ channels that do not function properly. An action potential of a normal fruit fly and a shaker mutant is shown below.
Which of the following statements (I - IV) could be possible explanations for the differences between the action potentials?
I. The faulty K+ channels don't open for as long so there is slower diffusion of K+ ions.
II. The faulty K+ channels may be opening early, preventing maximum depolarisation.
III. The faulty K+ channels cause K+ ions to diffuse back into the axon more slowly, resulting in slower repolarisation.
IV. In wild-type drosophila, the functioning K+ channels allow for a faster rate of depolarisation.