AQA GCSE Biology Biology Paper 2 (Foundation), June 2025: Question 1

9 marks · Low Demand difficulty · Short Answer

Define a dominant allele, determine phenotypes and genotypes in rabbits using a Punnett square, and predict sex chromosome distribution and offspring ratios.

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Question

Question text

01 Some people keep rabbits as pets.

Figure 1 shows two types of rabbit.

Figure 1

The fur colour pattern in the Himalayan rabbit is caused by a dominant allele.

01.1 What is a dominant allele?

[1 mark]

Tick ( ) one box.

An allele expressed only if a rabbit has two copies of the allele

An allele expressed only if it is inherited from the male rabbit

An allele expressed when a rabbit has only one copy of the allele4

In Questions 01.2 and 01.3, use the following symbols:

H = dominant allele for Himalayan fur pattern

h = recessive allele for white fur.

01.2 What is the genotype of a white rabbit?

[1 mark]

Tick ( ) one box.

HH Hh hh

A male Himalayan rabbit was crossed with a female Himalayan rabbit.

The male rabbit and the female rabbit each had the heterozygous genotype Hh.

Some of the offspring were Himalayan rabbits and some of the offspring were

white rabbits.

01.3 Complete the Punnett square diagram in Figure 2.

You should show:

• the male gametes

• the offspring genotypes.

[3 marks]

Figure 2

01.4 Some of the offspring in Figure 2 are homozygous and some are heterozygous.

Draw a ring around the genotype of one homozygous offspring in Figure 2.

*04* [1 mark]

01.5 Four offspring were born.

How many of the four offspring would you expect to be Himalayan rabbits?

Use Figure 2.

[1 mark]

Tick ( ) one box.

12 3 4

01.6 Inheritance of sex in rabbits is the same as inheritance of sex in humans.

A female rabbit has two X chromosomes in each body cell.

How many X chromosomes does a male rabbit have in each body cell?

[1 mark]

Tick ( ) one box.

01 2

01.7 Some of the offspring in Figure 2 would be male and some of the offspring would

be female.

How many of the four offspring in Question 01.5 would you predict to be female?

[1 mark]

Mark scheme

Show the mark scheme

Question 1

AO /

Question Answers Extra information Mark

Spec. Ref.

01.1 an allele expressed when a 1 AO1

rabbit has only one copy of the 4.6.1.6

allele

AO /

Spec. Ref.

01.2 hh 1 AO2

4.6.1.6

AO /

Spec. Ref.

01.3 AO2

H h 4.6.1.6

H HH Hh

h Hh hh

male gametes correct 1

all three offspring genotypes allow 1 mark for 2 correct 2

correctly derived from gametes

AO /

Spec. Ref.

01.4 (on Figure 2) AO2

4.6.1.6

ring drawn around HH and / or 1

AO /

Spec. Ref.

01.5 3 answer must be consistent with 1 AO3

genotypes in question 01.3 if 4.6.1.6

given

allow 3 if question 01.3 is not

answered

AO /

Spec. Ref.

01.6 1 1 AO1

4.6.1.8

AO /

Spec. Ref.

01.7 2 / two allow half / ½ (of them) 1 AO2

ignore ratios 4.6.1.8

Total Question 1 9

How to answer it

Inheritance of Coat Colour & Sex Determination

📋 What This Question Tests

This question assesses fundamental genetics knowledge from topic 4.6 (Inheritance, Variation and Evolution):

Defining dominant vs recessive alleles.
Determining genotypes and completing a Punnett square for a monohybrid cross.
Distinguishing between homozygous and heterozygous genotypes.
Predicting offspring phenotype numbers from genetic ratios.
Understanding mammalian sex chromosomes (XX vs XY) and the 50% probability of male/female offspring.

Part 01.1 • Definition of a Dominant Allele [1 Mark]

What is a dominant allele?

✅ Correct Answer

Tick the third box:

"An allele expressed when a rabbit has only one copy of the allele"

awarded for selecting the single correct statement.

💡 Key Knowledge

Dominant: Always expressed in the phenotype, even if only one copy is present (genotype HH or Hh ).
Recessive: Only expressed if two copies are present ( hh ) and no dominant allele is present.

❌ Common Errors

Confusing dominant with recessive (ticking "two copies").
Believing dominant alleles only come from the male parent (alleles have equal inheritance regardless of sex for autosomes).

Part 01.2 • Identifying Genotypes [1 Mark]

Genotype of a White Rabbit

✅ Correct Answer

Tick the third box: hh

awarded for selecting the homozygous recessive genotype.

🧠 Exam Technique

Read the symbols provided before the question carefully:

H = dominant allele (Himalayan)
h = recessive allele (white)

Because white is recessive, the rabbit must have two lowercase letters ( hh ) to look white.

Part 01.3 • Completing the Punnett Square [3 Marks]

Heterozygous Cross (Hh × Hh)

✅ Correct Completed Diagram

	Female
H	h
Male	H	HH	Hh
h	Hh	hh

Mark breakdown:
• 1 mark: Male gametes correct down the left side ( H and h )
• 2 marks: All 3 missing offspring genotypes correct ( Hh , Hh , hh )
(Allow 1 mark if 2 offspring genotypes are correct)

🧠 Exam Technique: Writing Letters

Ensure uppercase H and lowercase h look distinct to avoid losing marks for ambiguity.
Conventionally, write the capital letter first ( Hh rather than hH ), though both are technically accepted.

Part 01.4 • Homozygous vs Heterozygous [1 Mark]

Identifying a Homozygous Offspring

✅ Correct Answer

Draw a ring around either:

HH (homozygous dominant), OR
hh (homozygous recessive)

awarded for circling HH and/or hh on Figure 2.

💡 Key Knowledge: Prefix Clues

Homo- means "the same" → alleles are identical ( HH or hh ).
Hetero- means "different" → alleles are different ( Hh ).

Part 01.5 • Phenotype Prediction [1 Mark]

Expected Number of Himalayan Offspring

✅ Correct Answer

Tick the box for: 3

awarded for identifying 3 out of 4 offspring have the Himalayan phenotype.

📐 Step-by-Step Breakdown

Look at the four grid boxes: HH , Hh , Hh , hh .
Identify those with at least one dominant allele ( H ):
- HH → Himalayan
- Hh → Himalayan
- Hh → Himalayan
Only hh is white.
Total Himalayan = 3 (a 3:1 ratio).

❌ Common Errors

Students often mistake Hh for white or think only HH will show black patches. Because H is dominant, Hh always displays the Himalayan fur pattern.

Parts 01.6 & 01.7 • Sex Chromosomes and Ratios [2 Marks]

Mammalian Sex Inheritance

✅ Correct Answers

01.6: Tick the box for 1 [1 mark]

01.7: 2 (or "two", or "half" / "½") [1 mark]

💡 Key Knowledge: Sex Determination

Females have two X chromosomes: XX .
Males have one X and one Y chromosome: XY . Therefore, a male has exactly 1 X chromosome per cell.
Sex inheritance is always a 1 : 1 (50%) chance:
50% of 4 offspring = 2 females.

🧠 Exam Technique for 01.7

Notice the question asks "How many of the four offspring...", meaning the examiner wants an integer count (2), not a ratio like 1:1. The mark scheme explicitly states: "ignore ratios".

Topics

Biology · B6: Inheritance, Variation and Evolution

Question and mark scheme from the AQA GCSE Biology examination, Biology Paper 2 (Foundation), June 2025. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.