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Unit 7 AQA Unit 7
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AQA Biology A-Level - Inheritance and Hardy-Weinberg Principle QP PhysicsAndMathsTutor.comQ1.
In fruit flies, males have the sex chromosomes XY and the females have XX. In
fruit flies, a gene for eye colour is carried on the X chromosome. The allele for
red eyes, R, is dominant to the allele for white eyes, r.
(a) Male fruit flies are more likely than female fruit flies to have white eyes.
Explain why.
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(2)
(b) A female fruit fly with white eyes was crossed with a male fruit fly with red
eyes to produce a large number of offspring.
Tick (✓) one box next to the statement which correctly describes the
phenotypes produced from this cross.
All offspring red-eyed
All females red-eyed, all males
white-eyed
All males red-eyed, all females
white-eyed
All males white-eyed, females red-eyed
and females white-eyed
(1)
In fruit flies, the genes for body colour and for wing development are not on the
sex chromosomes. The allele for grey body colour, G, is dominant to the allele
for black body colour, g. The allele for long wings, L, is dominant to the allele for
short wings, l.
A geneticist carried out a cross between fruit flies with grey bodies and long
wings (heterozygous for both genes) and fruit flies with black bodies and short
wings.
Page 1 of 16
,AQA Biology A-Level - Inheritance and Hardy-Weinberg Principle QP PhysicsAndMathsTutor.com
The table below shows the results of this cross.
Phenotype of
Number of offspring
offspring
Grey body and long
223
wings
Black body and short
218
wings
(c) Explain the results in the table above.
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(3)
(d) The first generation of a population of fruit flies had 50 females.
Calculate how many female fruit flies would be produced from this
population in the fifth generation.
You can assume:
• each female produces 400 offspring each generation
• half the offspring produced each generation are female
• there is no immigration or emigration
• no flies die before reproducing.
Show your working.
Page 2 of 16
, AQA Biology A-Level - Inheritance and Hardy-Weinberg Principle QP PhysicsAndMathsTutor.com
Give your answer in standard form.
Answer _______________
(3)
(Total 9 marks)
Q2.
(a) Mutation is one cause of genetic variation in organisms.
Give two other causes of genetic variation.
1 __________________________________________________________
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2 __________________________________________________________
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(2)
In a species of flowering plant, the T allele for tallness is dominant to the t allele
for dwarfness. In the same species, two alleles CR (red) and CW (white) code for
the colour of flowers. When homozygous red-flowered plants were crossed with
homozygous white-flowered plants, all the offspring had pink flowers.
(b) Name the relationship between the two alleles that code for flower colour.
___________________________________________________________
(1)
(c) A dwarf, pink-flowered plant was crossed with a heterozygous tall,
white-flowered plant.
Complete the genetic diagram to show all the possible genotypes and the
ratio of phenotypes expected in the offspring of this cross.
Page 3 of 16
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