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OCR GCSE Combined Science

Topic questions Genetics and inheritance Sex determination

Sex determination

5 questions · 17 marks · about 20 minutes

Sex determination questions

TopicSex determination

OCR J250 Sex determination 5 questions

Biology Paper 2 June 2022 Foundation tier, Question 13 6 marks

(a)

A student models the inheritance of sex using two coins.

• The student puts a red sticker on both sides of one coin to represent a female.

• They then put a red sticker on one side and a white sticker on the other side of a second coin to represent a male.

Which of the two sex chromosomes is represented by each colour?

Red =........ chromosome

White =........ chromosome

[1]
Reveal mark scheme Mark scheme for question 13(a)
(b)

The student tosses the two coins 10 times and records the colour of the sticker showing on each coin.

The table shows their results.

Male coinFemale coinOffspring Boy (B) or Girl (G)?
redredG
redred
whitered
whitered
whitered
redred
whitered
whitered
redred
whitered

The offspring is determined by the colour recorded for each coin.

(b)(i)

Complete the column for the offspring. One has been done for you.

[1]
Reveal mark scheme Mark scheme for question 13(b)(i)
(b)(ii)

Calculate the ratio of boys to girls in the 10 offspring.

[1]
Reveal mark scheme Mark scheme for question 13(b)(ii)
(b)(iii)

The results do not match the expected ratio.

What is the expected ratio of offspring for boys: girls?

[1]
Reveal mark scheme Mark scheme for question 13(b)(iii)
(c)

Explain why the results do not match the expected ratio. Suggest how the student could develop the experiment to get closer to the expected result.

[2]
Reveal mark scheme Mark scheme for question 13(c)

Biology Paper 2 November 2021 Foundation tier, Question 3 1 mark

Which is the correct combination of chromosomes that determine sex in humans?

A XX in a female

B XX in a male

C XY in a female

D YY in a male

Question 3, shown as an image
[1]
Reveal mark scheme Mark scheme for question 3

Biology Paper 8 November 2021 Higher tier, Question 14 5 marks

(a)

The diagram shows two cells from a mosquito with a chromosome number of 6.

Different types of cell division produced Cell A and Cell B.

Figure for question 14

Name the type of cell division that produced Cell A and explain its importance for the mosquito.

Type of cell division........

[2]
Reveal mark scheme Mark scheme for question 14(a)
(b)

Sexual reproduction is important for species as it results in differences within a species.

(b)(i)

Within a species of mosquito there are some mosquito that need blood to lay eggs and others that do not.

Why is this an example of discontinuous variation?

[1]
Reveal mark scheme Mark scheme for question 14(b)(i)
(b)(ii)

What is the probability of a baby being male when humans sexually reproduce?

Complete the genetic diagram to explain your answer.

Figure for question 14
[2]
Reveal mark scheme Mark scheme for question 14(b)(ii)

Biology Paper 2 June 2019 Foundation tier, Question 5 1 mark

Which combination of sex chromosomes is correct for humans?

A female XX male XX

B female XY male XX

C female XX male XY

D female XX male YY

Question 5, shown as an image
[1]
Reveal mark scheme Mark scheme for question 5

Biology Paper 2 June 2018 Foundation tier, Question 15 4 marks

Three students model the determination of sex in humans.

They toss a coin 18 times and record the result.

The table shows the results and the ratio of the total heads: total tails.

TossOutcomeTotal headsTotal tailsRatio
1Heads101:0
2Heads202:0
3Tails212:1
4Heads313:1
5Heads414:1
6Heads515:1
7Tails525:2
8Tails535:3
9Heads632:1
10Heads737:3
11Tails747:4
12Tails757:5
13Heads858:5
14Tails868:6
15Heads963:2
16Heads106.............
17Tails10710:7
18Tails1085:4
(a)

The ratio for 16 is missing.

Calculate the ratio for 16 tosses.

[1]
Reveal mark scheme Mark scheme for question 15(a)
(b)

None of the ratios match the expected ratio of males to females you would show in a genetic cross.

Here are three statements about the results:

Student A – The ratio after five tosses is closest to the expected outcome.

Student B – The ratio after ten tosses is closest to the expected outcome.

Student C – The ratio after eighteen tosses is closest to the expected outcome.

Which statement is correct?

Explain your answer.

[2]
Reveal mark scheme Mark scheme for question 15(b)
(c)

The students want to improve the method to get a result that matches the expected ratio.

Write down one way to improve the method.

[1]
Reveal mark scheme Mark scheme for question 15(c)

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