2
The diagram shows a family tree in which some individuals have an inherited disorder, which
may cause serious long-term health problems.
(a)
(b)
J
K
D
E
Male without disorder
Key
Female without disorder
B
F
G
Male with disorder
What proportion of the children of A and B have the disorder?
M
Female with disorder
N
Explain the evidence from the diagram which shows that the allele for the disorder is
dominant.
Use the appropriate letters to identify individuals in your answer.
You may use genetic diagrams in your explanation. There is space for you to draw a
genetic diagram at the top of the facing page.
H
(1)