1 Huntington’s disease is a genetic disorder.

The genetic diagram shows the inheritance of this disorder.

parent 1 parent 2

Hh hh
h = normal allele

H h h h H = Huntington’s allele

Hh Hh hh hh
Huntington’s Huntington’s normal normal

(a) (i) Use words or letters from the box to complete the following sentences.
(2)

dominant recessive phenotype

h HH hh

Huntington’s disease is caused by a ............................................... allele.

People with Huntington’s disease can have the genotype Hh or .............................................. .
(ii) Complete the Punnett square to show the potential offspring of two parents
heterozygous for Huntington’s disease.
(2)

(iii) State the probability that a child of two parents, heterozygous for
Huntington’s disease, will have the disease.
(1)

. . . . . .................................. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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 (b) The genetic diagram shows the inheritance of cystic fibrosis.

parent 1 parent 2

Ff Ff
f = cystic fibrosis allele
F f F f F = normal allele

FF Ff Ff ff
normal carrier carrier cystic fibrosis

(i) Explain why, if both sets of parents are heterozygous, the chance of inheriting
Huntington’s disease is greater than the chance of inheriting cystic fibrosis.
(2)

. . . . . ................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........................................................................................................................................... . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . ................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........................................................................................................................................... . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . ................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........................................................................................................................................... . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . ................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........................................................................................................................................... . . . . . . . . . . . . . . . . . . . . . . . . . . .

(ii) Complete the sentence by putting a cross ( ) in the box next to your answer.
A symptom of cystic fibrosis is the overproduction of
(1)

A mucus
B red blood cells
C stomach acid
D white blood cells

(iii) Explain why a man with cystic fibrosis may be infertile.

(2)

. . . . . ................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........................................................................................................................................... . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . ................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........................................................................................................................................... . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . ................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........................................................................................................................................... . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . ................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........................................................................................................................................... . . . . . . . . . . . . . . . . . . . . . . . . . . .

(Total for Question 1 = 10 marks)

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2 Haemophilia is a recessive sex-linked disorder.

This family pedigree shows the inheritance of haemophilia.

A B
affected male

carrier female

unaffected male

unaffected female
C D

(a) (i) State the sex chromosomes of person B.

(1)

. . . .................................. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........................................................................................................................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(ii) Explain why the male offspring from A and B do not have haemophilia.
(2)

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. . . .................................. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........................................................................................................................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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 (iii) Using the Punnett square, calculate the probability that individuals C and D
could have a child with haemophilia.
(3)

. . . . . ..................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . ..................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . ..................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . ..................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . ..................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . ..................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . .

(b) Haemophilia can be treated using a blood clotting factor produced in a fermenter.
The conditions inside a fermenter have to be carefully controlled.
Explain why one named condition must be controlled in a fermenter.
(2)

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. . . . . ..................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . ..................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . ..................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . ..................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . ..................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . .

(Total for Question 2 = 8 marks)

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3 (a) The earlobes of an individual are detached or attached. This is determined by the
alleles inherited from their parents.

detached earlobe attached earlobe

An individual with attached earlobes must have inherited two recessive alleles
from each of their parents and will have the genotype ee.
(i) State the genetic term used to describe an individual with the genotype ee
for attached earlobes.
(1)

. . . . ................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........................................................................................................................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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 (ii) A female with the genotype ee has attached earlobes and a male with the
genotype Ee has detached earlobes.
Complete the Punnett square to show the gametes and genotypes of the
offspring for this female and male.
(2)

female gametes

male gametes

(iii) State the probability of the offspring having detached earlobes.

(1)

. . . .................................. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(iv)
i What is the percentage probability of a homozygous dominant mother and
homozygous recessive father producing a child with attached earlobes?
Put a cross ( ) in the box next to your answer.
(1)
A 0%
B 25%
C 75%
D 100%

PhysicsAndMathsTutor.com
 (b) Cystic fibrosis is a genetic disorder that is caused by the inheritance of two
recessive alleles.
Describe the symptoms of cystic fibrosis.
(3)

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. . . . . ................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(Total for Question 3 = 8 marks)

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4 (a) The graph shows the variation in eye colour in a human population.

30
28
26
24
number
of individuals 22
20
18
16
14
12
10
8
6
4
2
0
blue brown green grey hazel
eye colour

(i) How many individuals had their eye colour recorded in this human
population?

Put a cross ( ) in the box next to your answer.

(1)
A 7
B 27
C 30
D 40
(ii) Calculate the percentage of individuals with brown eyes in this human
population.
(2)

answer = .................................... %

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 (b) An individual’s eye colour is determined by the alleles they inherit from their
parents.

A female parent with the genotype (bb) had blue eyes and a male parent with the
genotype (Bb) had brown eyes.
(i) Complete the Punnett square to show the gametes of the parents and the
genotypes of the offspring.
(2)
Female gametes

Male gametes

(ii) If these two parents have one child, state the probability that this child would
have blue eyes.
(1)

. . ................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........................................................................................................................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(iii) Give the genetic term that describes the genotype (bb).
(1)

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(c) Variation may arise due to the geographic isolation of a species.

Explain how geographic isolation of members of one species can lead to a new
species evolving.
(3)

. . ................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........................................................................................................................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . ................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........................................................................................................................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . ................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........................................................................................................................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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. . ................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........................................................................................................................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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PhysicsAndMathsTutor.com (Total for Question 4 = 10 marks)

5 Cystic fibrosis is a genetic disorder caused by recessive alleles.

The diagram shows the inheritance of cystic fibrosis in a family.

generation

key
T female male
1 2 3 4
unaffected
individual
TT affected
1 2 individual

TTT
1 2 3 4 5 6

(a) (i) State the number of offspring in generation TTT who will have the disorder
cystic fibrosis.
(1)

................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........................................................................................................................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(ii) Complete the sentence by putting a cross ( ) in the box next to your answer.

In generation TTT, individual 3 is

(1)
A a carrier of the cystic fibrosis allele
B heterozygous for cystic fibrosis
C homozygous dominant for cystic fibrosis
D homozygous recessive for cystic fibrosis

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 (iii) Explain why both individuals in generation TT must be heterozygous for
cystic fibrosis.
(2)

................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........................................................................................................................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........................................................................................................................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........................................................................................................................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........................................................................................................................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(b) Complete the Punnett square to illustrate the inheritance of cystic fibrosis from
the two heterozygous parents in generation TT .

Use B for the dominant allele and b for the recessive allele.
(2)
female

male

(c) Explain why pedigree analysis would be important to the unaffected individuals in
generation TTT.

Use percentages or ratios to help illustrate this.

(2)

................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........................................................................................................................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........................................................................................................................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........................................................................................................................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........................................................................................................................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(Total for Question 5 = 8 marks)

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