Colour blindness in humans is the result of a defect in some of the light receptor cells in the retina of the eye. Rod cells and cone cells are the two kinds of light receptor.
(a)[3]
Fill in Table 3.1 to state the function of three cell types in the eye.
(b)[5]
Use Fig. 3.1 to describe and explain how rod cells and cone cells are arranged across the retina.
(c)[2]
Describe evidence from Fig. 3.2 that indicates colour blindness is a sex-linked characteristic.
(d)[4]
Complete the genetic diagram to work out the probability that the baby will be colour-blind.
Worked solution & mark scheme
This 14-mark question has a full step-by-step worked solution and mark scheme. One marking point: “rod cells - vision at night / detects low light” …