Monohybrid inheritance — Paper 2 · IGCSE Sciences - Co-ordinated (Double) 0654

8 In a plant, the allele for red flowers is dominant to the allele for yellow flowers. A heterozygous red-flowered plant is crossed with a homozygous yellow-flowered plant. Which statement about the offspring is correct? A 25% will have red flowers, 75% will have yellow flowers. B 50% will have red flowers, 50% will have yellow flowers. C 75% will have red flowers, 25% will have yellow flowers. D 100% will have red flowers, 0% will have yellow flowers.

1 marks

Answer: B

This question in 0654/23 May/June 2017

13 In a species of plant, the allele for yellow flowers is dominant to the allele for red flowers. Two heterozygous yellow-flowered plants are crossed. Which offspring are produced? A 25% with yellow flowers, 75% with red flowers B 50% with yellow flowers, 50% with red flowers C 75% with yellow flowers, 25% with red flowers D 100% with yellow flowers

1 marks

Answer: C

This question in 0654/23 Oct/Nov 2017

11 A man breeds small mammals in which the fur colour is black or white. The allele for white is dominant to black. If he chooses a pair of heterozygous white mammals to breed together, which proportion of the offspring mammals will be black? A none of them B about a quarter C about half D all of them

1 marks

Answer: B

This question in 0654/22 Oct/Nov 2018

11 In pea plants, the allele for purple flowers is dominant to the allele for white flowers. Two heterozygous purple-flowered plants are crossed. What will be the expected flower colour of the offspring plants? A all purple B all white C 1 purple : 1 white D 3 purple : 1 white

1 marks

Answer: D

This question in 0654/23 Oct/Nov 2018

11 The diagram shows the inheritance of a disease. key unaffected female unaffected male affected female affected male Which row is correct for the parents and the allele for the disease? allele for the parents disease A heterozygous dominant B heterozygous recessive C homozygous dominant D homozygous recessive

1 marks

Answer: B

This question in 0654/23 May/June 2020

11 Which term is used to describe an individual with two of the same allele for a characteristic? A genotype B heterozygous C homozygous D phenotype

1 marks

Answer: C

This question in 0654/21 Oct/Nov 2020

11 The pedigree diagram shows the inheritance of a recessive condition. key P Q male without condition male with condition R female without condition female with condition Which statements are correct with reference to this condition? 1 P and Q are both heterozygous for the condition. 2 Q and R have different genotypes. 3 P and R have the same genotype. A 1 and 2 only B 1 and 3 only C 2 and 3 only D 1, 2 and 3

1 marks

Answer: A

This question in 0654/23 Oct/Nov 2020

11 The allele for long fur in cats is recessive to the allele for short fur. The pedigree diagram shows the inheritance of long and short fur in a family of cats. key male with long fur male with short fur female with long fur female with short fur How many cats in the pedigree diagram are heterozygous for fur length? A 2 B 4 C 5 D 6

1 marks

Answer: D

This question in 0654/21 May/June 2021

11 Two rabbits with floppy ears were crossed and produced three offspring. The pedigree diagram of the cross is shown. key floppy eared female 1 2 floppy eared male straight eared female straight eared male 3 Which row is correct for this cross? genotype of 1 genotype of 2 dominant allele A heterozygous heterozygous floppy ears B homozygous homozygous floppy ears C heterozygous heterozygous straight ears D homozygous homozygous straight ears

1 marks

Answer: A

This question in 0654/22 May/June 2021

11 Wing length in fruit flies is controlled by a single pair of alleles. The diagram shows the results of crosses between fruit flies. 1 2 key male with short wings male with long wings 3 4 5 6 7 female with short wings female with long wings 8 9 What is the probability of individuals 6 and 7 producing another offspring with long wings? A 12.5% B 25% C 50% D 75%

1 marks

Answer: C

This question in 0654/21 Oct/Nov 2021

11 The pedigree diagram shows inheritance of a disease caused by a dominant allele. 1 key affected male 2 3 unaffected male affected female 4 unaffected female Which statement is correct? A Individual 1 is homozygous dominant. B Individual 2 is homozygous dominant. C Individual 3 is homozygous recessive. D Individual 4 is heterozygous.

1 marks

Answer: C

This question in 0654/22 Oct/Nov 2021

11 Cystic fibrosis is a genetic disease caused by a recessive allele. key affected male unaffected male affected female unaffected female What is the genetic composition of the parents? male parent female parent A heterozygous heterozygous B heterozygous homozygous C homozygous heterozygous D homozygous homozygous

1 marks

Answer: C

This question in 0654/21 May/June 2022

11 Cats with polydactyly have an extra digit on their paw. The allele for polydactyly, P, is dominant to the allele for having five digits, p. The pedigree diagram shows a family of cats where polydactyly is present. key 1 2 male with polydactyly male without polydactyly 3 4 female with polydactyly female without polydactyly 5 6 What is the probability that the next kitten from the mating of 3 and 4 has five digits? A 0.00 B 0.25 C 0.50 D 0.75

1 marks

Answer: C

This question in 0654/21 Oct/Nov 2023

11 Cystic fibrosis is a genetic condition. The allele for cystic fibrosis is recessive. The diagram shows inheritance of cystic fibrosis in a family. key male non-sufferer male sufferer female non-sufferer female sufferer What is the chance of the next child having cystic fibrosis? A 0% B 25% C 75% D 100%

1 marks

Answer: B

This question in 0654/22 Feb/March 2024

11 The diagram shows the inheritance of a disease. key unaffected female unaffected male affected female affected male Which row is correct for the parents and the allele for the disease? allele for the parents disease A heterozygous dominant B heterozygous recessive C homozygous dominant D homozygous recessive

1 marks

Answer: B

This question in 0654/21 May/June 2024

11 Horn development in some cattle is controlled by a pair of alleles. The allele for not developing horns is dominant to the allele for developing horns. The pedigree diagram shows cattle with and without horns. key male without horns male with horns female without horns female with horns How many of the cattle are definitely heterozygous? A 2 B 3 C 4 D 5

1 marks

Answer: C

This question in 0654/21 Oct/Nov 2024

11 The pedigree diagram shows the inheritance of a recessive condition. key P Q male without condition male with condition R female without condition female with condition Which statements are correct with reference to this condition? 1 P and Q are both heterozygous for the condition. 2 Q and R have different genotypes. 3 P and R have the same genotype. A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D 2 and 3 only

1 marks

Answer: C

This question in 0654/22 Oct/Nov 2024

12 Polydactyly is a condition that causes babies to be born with extra fingers or toes. The allele that causes polydactyly is dominant. key affected female unaffected female affected male unaffected male How many individuals on the pedigree diagram are heterozygous for polydactyly? A 5 B 6 C 7 D 8

1 marks

Answer: B

This question in 0654/22 Feb/March 2025

11 Polydactyly is the possession of additional fingers or toes. It is caused by a dominant allele. The pedigree diagram shows the inheritance of polydactyly by a family. key male with polydactyly female with polydactyly male without polydactyly female without polydactyly How many people in this family are heterozygous? A 3 B 4 C 6 D 7

1 marks

Answer: B

This question in 0654/21 May/June 2025

12 Which row shows the monohybrid crosses that produce predicted phenotype ratios of 1 : 1 and 3 : 1? 1 : 1 ratio 3 : 1 ratio A AA  aa Aa  aa B Aa  Aa Aa  aa C Aa  aa Aa  Aa D Aa  aa AA  Aa

1 marks

Answer: C

This question in 0654/23 Oct/Nov 2025