1 In fruit flies, the length of the wings is controlled by a gene with two alleles.

The
allele for long wings (L) is dominant to the allele for short wings (l). The diagram
shows a long-winged fruit fly and a short-winged fruit fly.

long-winged fruit fly short-winged fruit fly

(a) Complete the table by writing the genotype, the description of genotype and the
phenotype of the fruit flies.
(3)

Genotype Description of genotype Phenotype

LL homozygous dominant

Ll heterozygous

short-winged
(b) Two heterozygous fruit flies mated. The number of long-winged and short-winged
offspring produced are shown below.

Long-winged offspring Short-winged offspring

612 204

Tick one box to show the number of these offspring that is likely to be heterozygous.
(1)

Number Tick

204

408

612

816

(c) Yeast cells feed on rotting fruit. Fruit flies feed on these yeast cells.
Use this information to draw a food chain in the space below.
(2)
 (d) A student wanted to find out if fruit flies are attracted to rotting fruit. He set up
this apparatus.

lid

glass tank

fresh fruit rotting fruit

He released 20 fruit flies into the glass tank. After ten minutes, he counted the
number of fruit flies found near the fresh fruit and the number found near the
rotting fruit. The table shows his results.

Number of fruit flies counted after ten minutes

near fresh fruit near rotting fruit

4 16

(i) Name two factors that the student should control in this investigation.
(2)

1 . .................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........................................................................................................................................... . . . . . . . .. . . . . . . . . . . . . . . . . . .

2 . .................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........................................................................................................................................... . . . . . . . .. . . . . . . . . . . . . . . . . . .
(ii) Do you think the student’s results are reliable?
Give a reason for your answer.
(1)

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

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

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

(Total for Question = 9 marks)

2 In mammals, males have two different sex chromosomes (X and Y) and females have
two similar sex chromosomes (X and X).
However, in birds males have two similar sex chromosomes (Z and Z), while females
have two different sex chromosomes (Z and W).
(a) Complete the genetic diagram to show how sex is inherited in birds.
(4)

Genotype of male parent Genotype of female parent

Gametes from male parent Gametes from female parent

Genotypes of offspring

Sex of offspring
 (b) In birds, the egg is extremely large and contains food molecules that the growing
embryo needs in order to develop.

(i) Suggest one food molecule that is present in a bird’s egg and describe the
role of this molecule in the growth of the bird embryo.
(2)

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

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

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

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

(ii) Suggest an advantage of the shell of the egg being made of a hard substance.
(1)

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

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

(iii) Chicken eggs are a rich source of vitamin A.

Give another source of vitamin A and describe the function of vitamin A in
humans.
(2)

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

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

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

. . . . .................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . .. . . . . . . . . . . . . . . . . . . . . .
 (c) The number of chromosomes in eggs and in sperm is less than the number of
chromosomes in the body cells of animals.
Explain how the number of chromosomes in animals is maintained in their offspring.
(3)

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

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

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

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

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

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

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

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

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

(Total for Question = 12 marks)

3 Achondroplasia is an inherited condition in humans. Adults with achondroplasia are
much shorter than average height.
This condition is controlled by a gene with two alleles. The dominant allele (A) codes
for shorter than average height and the recessive allele (a) codes for average height.
(a) Two parents both had achondroplasia. They had a child who grew up to be of
average height.
Use a genetic diagram to show:
x the genotype of each parent
x the gametes they produced
x the genotypes of all the possible offspring
x the phenotypes of all the possible offspring
(4)
 (b) The parents had a second child.
State the probability that this child grew up to be of average height.
(1)

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

(c) Achondroplasia is caused by a dominant allele.

(i) Explain what is meant by the term dominant allele.
(2)

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

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

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

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

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

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

(ii) Suggest why the number of people with achondroplasia is low, even though it
is a dominant condition.
(2)

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

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

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

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

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

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

(Total for Question = 9 marks)

4 (a) There are several different stages during the process of human reproduction. Some of
these stages are shown in the box.

baby embryo fetus gametes zygote

Complete the table by writing the name of the stages in each empty box to show
the correct order in which they occur.
(4)
Order Name of stage

5
 (b) The diagram shows a section through the heart of a fetus. The arrows show the
direction of blood flow.

left ventricle

right ventricle

Describe two differences, shown in the diagram, between the heart of a fetus and
an adult heart.
(2)

1 ................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........................................................................................................................................... . . . . . . . . . . .. . . . . . . . . . . . . . . . .

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

2 ................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........................................................................................................................................... . . . . . . . . . . .. . . . . . . . . . . . . . . . .

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

(c) The sex chromosomes in the cells of a mother are XX. The sex chromosomes in
the cells of a father are XY.
(i) Use this information to give the sex chromosomes in the cells of their male fetus.
(1)

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

(ii) Give the number of chromosomes in a body cell of the male fetus.
(1)

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

(Total for Question = 8 marks)

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