Monohybrid inheritance — Paper 2 · IGCSE Biology (9-1) 0970

32 The diagram shows the phenotypes for blood groups in a family. parents A B key male female children A AB O Which statement about the genotypes of the parents is correct? A Both parents have alleles for blood group A and B. B Both parents have the allele for blood group O. C Only the father has the allele for blood group O. D Only the mother has the allele for blood group O.

1 marks

Answer: B

This question in 0970/21 May/June 2018

33 Sickle-cell anaemia is a genetic disorder which results in severe illness in homozygous individuals. In some human populations being heterozygous can be beneficial. What could be the reason for this? A Heterozygous individuals are not affected by the disorder. B Heterozygous individuals are more resistant to malaria. C It is caused by a dominant allele. D The disorder is sex-linked.

1 marks

Answer: B

This question in 0970/21 May/June 2018

32 Pure-breeding black-feathered chickens are mated with pure-breeding white-feathered chickens. All of the individuals in the offspring in the F1 generation have both black and white feathers. What will be the ratio of offspring phenotypes when two of the F1 generation chickens are crossed? A 1 black : 1 white B 1 black : 2 black and white : 1 white C 3 white : 1 black D 3 black : 1 white

1 marks

Answer: B

This question in 0970/22 Oct/Nov 2018

34 Which statement is correct? A People who are heterozygous for the sickle-cell allele have a resistance to malaria. B Sickle-cell anaemia is caused by a change in the amino acid sequence of the haemoglobin gene. C Sickle-cell anaemia is caused by both genetic and environmental factors interacting. D The sickle-cell allele is rare in human populations in areas where there is malaria.

1 marks

Answer: A

This question in 0970/22 May/June 2019

32 The diagram shows a genetic cross between a male bird with black feathers and a female bird with white feathers. All of the offspring have blue feathers. parents FBFB × FWFW black white offspring FBFW 100% blue Two of the blue offspring are crossed. Which row shows the correct phenotype percentages for the cross? percentage percentage percentage black blue white A 25 75 0 B 25 50 25 C 50 20 25 D 75 0 25

1 marks

Answer: B

This question in 0970/22 Oct/Nov 2019

33 The graph shows the masses of two different types of tomato. type 1 type 2 number of tomatoes 0 20 40 60 80 100 120 140 160 180 200 220 240 mass / g What can be concluded from the graph? A Genes do not affect the mass of tomatoes. B Type 1 tomatoes show continuous variation. C Type 2 tomatoes are sometimes smaller than type 1 tomatoes. D Type 2 tomatoes show discontinuous variation.

1 marks

Answer: B

This question in 0970/21 May/June 2020

32 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 0970/22 May/June 2020

32 In guinea pigs, the allele for black fur is dominant and the allele for white fur is recessive. A test cross can be used to determine the genotype of a black guinea pig. What would be the expected result of the test cross if the black guinea pig was heterozygous? A 50% black, 50% white B 25% black, 75% white C 100% black D 100% white

1 marks

Answer: A

This question in 0970/22 Oct/Nov 2020

34 Colour blindness is a characteristic that is sex-linked. Which statement about colour blindness is correct? A The gene for colour blindness is located on the Y chromosome and colour blindness is more common in males than in females. B The gene for colour blindness is located on the X chromosome and colour blindness is more common in males than in females. C The gene for colour blindness is located on the X chromosome and colour blindness is more common in females than in males. D The gene for colour blindness is located on the Y chromosome and colour blindness is more common in females than in males.

1 marks

Answer: B

This question in 0970/21 May/June 2021

34 Coat colour in cattle is controlled by two codominant alleles. The genotype CRCR results in cattle with a red coloured coat. The genotype CWCW results in cattle with a white coloured coat. The genotype CRCW results in a roan coat; these cattle have a mixture of red hairs and white hairs in their coat. A mating occurs between a red cow and a roan bull. What is the expected ratio of coat colour in the offspring? A 50% red, 50% white B 100% red C 50% red, 50% roan D 100% roan

1 marks

Answer: C

This question in 0970/22 May/June 2021

32 The gene for haemophilia is found on the X chromosome and the allele for haemophilia is recessive. In the pedigree diagram the dominant allele is shown as XH and the recessive allele is shown as Xh. XHXh XHY key female male M N What is the probability of child M having haemophilia? A 0.00 B 0.25 C 0.50 D 1.00

1 marks

Answer: C

This question in 0970/22 Oct/Nov 2021

33 Sickle cell anaemia is a genetic disorder which results in severe illness in homozygous individuals. In some human populations, being heterozygous can be beneficial. What could be the reason for this? A Heterozygous individuals are not affected by the disorder. B Heterozygous individuals are more resistant to malaria. C The disorder is caused by a dominant allele. D The disorder is sex-linked.

1 marks

Answer: B

This question in 0970/21 May/June 2022

31 When a horse with red hair (genotype HRHR) breeds with a horse with white hair (genotype HWHW) the offspring have red and white hair (genotype HRHW). These horses are described as having roan-coloured hair. This is an example of codominance. When two horses with roan-coloured hair are bred together, what is the chance of their offspring also having roan-coloured hair? A 100% B 75% C 50% D 25%

1 marks

Answer: C

This question in 0970/22 May/June 2022

33 Sickle cell anaemia is a genetic disorder which results in severe illness in homozygous individuals. In some human populations, being heterozygous can be beneficial. What could be the reason for this? A Heterozygous individuals are not affected by the disorder. B Heterozygous individuals are more resistant to malaria. C The disorder is caused by a dominant allele. D The disorder is sex-linked.

1 marks

Answer: B

This question in 0970/22 May/June 2022

31 A sex-linked condition is caused by a recessive allele. A healthy male and female are both unaffected by the condition but the female has one copy of the recessive allele. What is the chance of their offspring being affected by the sex-linked condition? A 50% of all their offspring B 100% of male offspring and 0% of female offspring C 25% of all their offspring D 50% of male offspring and 25% of female offspring

1 marks

Answer: C

This question in 0970/22 Oct/Nov 2022

31 Which parents could produce offspring with blood group O? A heterozygous father with blood group A and heterozygous mother with blood group B B heterozygous father with blood group A and homozygous mother with blood group B C homozygous father with blood group A and heterozygous mother with blood group B D homozygous father with blood group A and homozygous mother with blood group O

1 marks

Answer: A

This question in 0970/21 May/June 2023

32 The diagram shows the inheritance of albinism in one family. Albinism is an inherited condition caused by a recessive allele. 1 2 key unaffected male unaffected female 3 4 5 6 male with albinism female with albinism 7 8 Which individuals must be heterozygous for this condition? A 1 and 2 B 4 and 7 C 5, 6 and 7 D 5 and 6 only

1 marks

Answer: C

This question in 0970/21 May/June 2023

31 A man of genotype IAIo and woman of genotype IBIo have a child. What is the chance that the child will have the same blood group as one of its parents? A zero B 1 in 4 C 1 in 2 D 3 in 4

1 marks

Answer: C

This question in 0970/22 May/June 2023

32 A man who has red-green colour blindness has a child with a woman who does not have red-green colour blindness. The child has red-green colour blindness. The man and woman decide to have another child. What is the percentage probability that their next child will have red-green colour blindness? A 0% B 25% C 50% D 100%

1 marks

Answer: C

This question in 0970/22 May/June 2023

38 Red-green colour blindness is a sex-linked characteristic caused by a recessive allele. Which prediction can be made about the children of a woman who is colour-blind and a man with normal vision? A Boys will be colour-blind, and girls will have a 50% chance of being colour-blind. B Boys will be colour-blind, and girls will have normal vision. C Girls will be colour-blind, and boys will have a 50% chance of being colour-blind. D Girls will be colour-blind, and boys will have normal vision.

1 marks

Answer: B

This question in 0970/22 Oct/Nov 2023

34 The pedigree diagrams show the pattern of inheritance of a genetic disorder in four families. This genetic disorder is not sex-linked. Which pedigree diagram proves that the genetic disorder must be caused by a dominant allele? A B C D key unaffected male unaffected female affected male affected female

1 marks

Answer: D

This question in 0970/21 May/June 2024

30 A farmer bred together male cattle with white hair and female cattle with red hair. All the offspring produced had roan hair (a mixture of red and white). He then repeatedly bred together two roan cattle, and the offspring were in the ratio of 1 red : 2 roan : 1 white. What explains why the farmer obtained this ratio? A The red phenotype is dominant to the white phenotype. B The roan phenotype is an example of codominance. C The roan phenotype is dominant to the red phenotype and the white phenotype. D The white phenotype is dominant to the red phenotype.

1 marks

Answer: B

This question in 0970/21 May/June 2025

31 The diagram shows the inheritance of a genetic condition in one family. key female with condition female without condition male with condition male without condition What can be concluded about this genetic condition? A The alleles for the condition must be codominant. B It is caused by a dominant allele. C It is caused by recessive alleles. D The alleles for the condition must be sex-linked.

1 marks

Answer: B

This question in 0970/22 May/June 2025

32 The photograph shows a speckled chicken. Speckled chickens have white feathers and black feathers. When a chicken with only white feathers and a chicken with only black feathers are crossed, all of the offspring are speckled. What would be the expected phenotypic ratio if a speckled chicken was crossed with a chicken with only white feathers? A all offspring have only white feathers B all offspring are speckled C 1 white feathers only : 1 speckled D 3 white feathers only : 1 speckled

1 marks

Answer: C

This question in 0970/22 Oct/Nov 2025