Monohybrid inheritance — Paper 1 · IGCSE Biology (9-1) 0970

32 The diagram shows the inheritance of sex in humans. male gametes X Y female X XX XY gametes X XX XY What is the chance of the couple’s next child being male? A 25% B 50% C 75% D 100%

1 marks

Answer: B

This question in 0970/11 May/June 2018

31 The allele for detached earlobes is dominant to the allele for attached earlobes. Two parents are heterozygous for detached earlobes. What is the probability of their first child having attached earlobes? A 0% B 25% C 50% D 75%

1 marks

Answer: B

This question in 0970/12 Oct/Nov 2018

30 A man has three sons. What is the chance of his next child being a daughter? A 0% B 25% C 50% D 100%

1 marks

Answer: C

This question in 0970/12 Oct/Nov 2019

32 In a plant species, the allele for red flowers, R, is dominant to the allele for white flowers, r. Homozygous red-flowered plants, RR, are crossed with homozygous white-flowered plants, rr. What is the colour of the flowers produced by the offspring of this cross? A all red B all white C equal numbers of red and white D three white to one red

1 marks

Answer: A

This question in 0970/12 Oct/Nov 2019

33 Pea plants produce either yellow or green seeds. Yellow (Y) is dominant to green (y). What are the most likely phenotypes of the offspring of a cross between YY and Yy plants? A 50% yellow and 50% green B 75% yellow and 25% green C 100% yellow D 100% green

1 marks

Answer: C

This question in 0970/11 May/June 2020

32 Which statement about the human sex chromosomes is correct? A Females have an X chromosome and a Y chromosome. B Females have two Y chromosomes. C Males and females have at least one X chromosome. D Males and females have at least one Y chromosome.

1 marks

Answer: C

This question in 0970/12 May/June 2020

33 The diagram shows the inheritance of height in pea plants. tall parent plant dwarf parent plant TT tt tall offspring plant tall offspring plant Tt Tt Which plants have a heterozygous genotype? A both parent plants B dwarf parent plant only C both offspring plants D tall parent plant only

1 marks

Answer: C

This question in 0970/12 May/June 2020

33 Which term is used to describe alleles that are always expressed when they are present in the genotype? A dominant B heterozygous C homozygous D recessive

1 marks

Answer: A

This question in 0970/12 Oct/Nov 2020

33 Which of these determine the sex of humans? A X and Y genes B X and Y alleles C X and Y chromosomes D X and Y genotypes

1 marks

Answer: C

This question in 0970/12 Oct/Nov 2021

34 A student used a diagram to explain the inheritance of sex in humans. mother father   eggs sperm   1 2 Which statements should she use to complete boxes 1 and 2? box 1 box 2 A all have an X chromosome half have an X chromosome and half have a Y chromosome B all have a Y chromosome half have an X chromosome and half have a Y chromosome C half have an X chromosome and all have an X chromosome half have a Y chromosome D half have an X chromosome and all have a Y chromosome half have a Y chromosome

1 marks

Answer: A

This question in 0970/11 May/June 2022

32 The diagram shows the inheritance of sex in humans. male gametes X Y female X XX XY gametes X XX XY A man and a woman have one female child. What is the chance of the couple’s next child being female? A 25% B 50% C 75% D 100%

1 marks

Answer: B

This question in 0970/12 May/June 2022

33 In rabbits, the allele for dark fur, R, is dominant to the allele for white fur, r. The diagram shows a cross between a rabbit with dark fur and a rabbit with white fur. × What are the genotypes of the parents? A Rr and rr B RR and rr C RR and Rr D R and r

1 marks

Answer: A

This question in 0970/12 May/June 2022

33 In one species of plant, the allele for red-coloured fruit is dominant and is represented by the letter R. The allele for white-coloured fruit is recessive and is represented by the letter r. Two plants that are heterozygous for fruit colour are crossed. What are the possible genotypes of the offspring plants from this cross? A RR, Rr and rr B all Rr C all rr D Rr and rr only

1 marks

Answer: A

This question in 0970/12 Oct/Nov 2022

34 A man has three sons. What is the chance of his next child being a daughter? A 0% B 25% C 50% D 100%

1 marks

Answer: C

This question in 0970/11 May/June 2023

33 When breeding, which pair of parents will be pure-breeding for a particular characteristic? A a heterozygous and a homozygous individual B two heterozygous individuals C two homozygous individuals D two individuals with the same phenotype

1 marks

Answer: C

This question in 0970/12 May/June 2023

34 In a pea plant, the allele for round seeds, R, is dominant to the allele for wrinkled seeds, r. If plants with the genotype Rr are crossed, what are the likely proportions of offspring? A all with round seeds B all with wrinkled seeds C 1 with round seeds : 1 with wrinkled seeds D 3 with round seeds : 1 with wrinkled seeds

1 marks

Answer: D

This question in 0970/12 May/June 2023

33 Two parents have the genotypes Bb and bb for a particular feature. What is the probability of these parents having offspring that are homozygous recessive for this feature? A 100% B 75% C 50% D 25%

1 marks

Answer: C

This question in 0970/12 Oct/Nov 2023

34 A genetic cross between two organisms may be shown as Tt  Tt. What does T represent? A a dominant allele B a dominant chromosome C a recessive allele D a recessive chromosome

1 marks

Answer: A

This question in 0970/12 Oct/Nov 2023

37 When white-flowered pea plants are crossed with red-flowered pea plants, the offspring plants all have red flowers. If these offspring plants are crossed, the next generation of plants contains both red-flowered and white-flowered plants. Which statement explains this? A The allele for red flowers is dominant, and the offspring plants are heterozygous. B The allele for red flowers is dominant, and the offspring plants are homozygous. C The allele for red flowers is recessive, and the offspring plants are heterozygous. D The allele for red flowers is recessive, and the offspring plants are homozygous.

1 marks

Answer: A

This question in 0970/12 Oct/Nov 2024

30 Cystic fibrosis is an inherited condition that occurs when an individual is homozygous for the recessive allele. If both parents are heterozygous for this characteristic, what is the probability that their first child will have cystic fibrosis? A 0% B 25% C 50% D 100%

1 marks

Answer: B

This question in 0970/12 May/June 2025

29 In a species of mammal, the allele for short hair, H, is dominant and the allele for long hair, h, is recessive. A heterozygous individual breeds with a long-haired individual. What is the expected ratio of the phenotypes in the offspring? A 100% short-haired, 0% long-haired B 75% short-haired, 25% long-haired C 50% short-haired, 50% long-haired D 25% short-haired, 75% long-haired

1 marks

Answer: C

This question in 0970/12 Oct/Nov 2025