Agenetic form of "night blindness" (i. e. poor vision in dim light) is caused by mutations in genes encoding rhodopsin kinase (rk) and arrestin. the mutations reduce the dynamic range of light perception, and the affected individuals have a prolonged light response and adapt very slowly to low light (when entering a dark theater room, for example). which of the following mutations do you expect to be the cause? a. loss-of-function rk mutations and loss-of-function arrestin mutations b. loss-of-function rk mutations and gain-of-function arrestin mutations c. gain-of-function rk mutations and loss-of-function arrestin mutations d. gain-of-function rk mutations and gain-of-function arrestin mutations

The answer is A - Loss-of-function RK mutations and loss-of-function arrestin mutations

Explanation:

RK is Rhodopsin Kinase. Rods which are photoreceptors (along with cones) for providing vision to the eyes contain a receptor-protein called Rhodopsin. When light hits the rhodopsin some changes occur which generate electrical signals that are carried through the optic nerve to the brain.

Mutation in Rhodopsin kinase is associated with night blindness

Humans with defects in RK, or its downstream regulator arrestin, have a prolonged light response, incapable of adapting quickly to sudden drops in ambient light intensity

b tumor cells have a cell wall instead of a membrane

explanation:

tumor cells different from normal cells because tumor cells have a cell wall instead of a membrane.