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CAIE A Level Biology 9700

Inheritance questions

Exam-style questions on Inheritance, ordered from foundation to challenge. Pick one, write your answer the way you would in the exam, and it comes back marked against the mark scheme, point by point.

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Written by Markquill to follow the Cambridge International syllabus. Markquill is independent and is not affiliated with or endorsed by Cambridge International.

  1. Outline4 marksStandardIn plants, the hormone gibberellin promotes stem elongation by causing the breakdown of DELLA repressor proteins. In bacteria, the lac operon controls the production of enzymes needed to metabolise lactose. Outline the…
  2. Describe4 marksStandardIn a eukaryotic cell, a transcription factor called TF-A binds to a specific enhancer sequence located upstream of a target gene. Describe how TF-A increases the rate of transcription of that target gene.
  3. Explain4 marksStandardA plant species has a diploid chromosome number of 6 (2n = 6). During meiosis, both crossing over and random orientation of homologous chromosomes occur. Explain how these two processes contribute to the production of…
  4. Describe5 marksStandardIn a species of flowering plant, the diploid (2n) chromosome number is 14. Describe the behaviour of chromosomes during meiosis I in a cell from this plant, and explain why a reduction division is necessary before…
  5. Explain5 marksStandardThe lac operon in Escherichia coli is a classic model of gene regulation in prokaryotes. (a) With reference to this operon, explain the difference between a structural gene and a regulatory gene. (b) Using the lac…
  6. Outline5 marksStandardOutline how the random fusion of gametes at fertilisation, together with the events of meiosis, leads to genetic variation in the offspring of a diploid organism.
  7. Explain4 marksStandardExplain how the presence of lactose switches on the lac operon in E. coli. In your answer, refer to the roles of regulatory and structural genes, and state whether the enzyme produced is inducible or repressible.
  8. Explain5 marksStandardIn a species of beetle, body colour is determined by two unlinked genes, E and M. The dominant allele E produces melanin; the recessive allele e results in no melanin, giving a pale body. The dominant allele M causes…
  9. Outline5 marksStandardIn a species of diploid mammal, males produce sperm and females produce eggs via meiosis. The gametes from each individual are genetically diverse due to crossing over and independent assortment during meiosis. Outline…
  10. Outline4 marksStandardIn a study of stem elongation in a plant species, researchers identified a mutant that lacks the DELLA protein. This mutant shows continuous stem elongation even in the absence of gibberellin. Outline the mechanism by…
  11. Explain5 marksStandardA species of beetle has a diploid chromosome number of 8. Two of its chromosome pairs, pair 1 and pair 2, are homologous. The beetle is heterozygous for two unlinked genes: gene A (alleles A and a) on pair 1 and gene B…
  12. Determine4 marksStandardAlbinism in humans is caused by a recessive allele of the TYR gene, which codes for the enzyme tyrosinase. Individuals with two copies of the recessive allele lack functional tyrosinase and have albinism. The dominant…
  13. Explain4 marksStandardIn a plant species, flower colour is controlled by two unlinked genes. Gene P (alleles P and p) controls pigment production; P gives coloured flowers, pp gives white flowers. Gene Q (alleles Q and q) controls pigment…
  14. Describe4 marksStandardA student prepared slides of cells from a grasshopper testis and observed four distinct stages of meiosis. The student's notes are shown below: Cell X: Homologous chromosomes are aligned in pairs on the equatorial…
  15. Describe5 marksStandardA student investigates the regulation of two enzymes in the bacterium Bacillus subtilis. Enzyme P is involved in breaking down the disaccharide lactulose. Enzyme Q is involved in the synthesis of the amino acid…
  16. Outline5 marksStandardIn a bacterial species, the enzymes for lactose metabolism (β-galactosidase and permease) are produced when lactose is present in the growth medium, but not when lactose is absent. (a) Outline the genetic control of…
  17. Describe5 marksStandardIn a dihybrid cross involving seed colour (yellow Y dominant over green y) and seed shape (round R dominant over wrinkled r), two heterozygous plants (YyRr) were crossed. The F2 generation produced the following…
  18. Explain4 marksStandardExplain how the presence of lactose leads to the expression of the lac structural genes in E. coli. In your answer, refer to the roles of regulatory and structural genes, and explain why the lac operon is described as…
  19. Outline4 marksStandardA student is given two photomicrographs of cells from the same plant species undergoing meiosis. Both cells are in anaphase. Cell A shows chromosomes moving to opposite poles; each chromosome appears as two chromatids…
  20. Determine5 marksStandardHaemophilia in humans is caused by an X-linked recessive allele. A woman whose father had haemophilia (but whose mother had no family history of the condition) is expecting a child with a man who has no family history…
  21. Outline4 marksStandardA student examines a photomicrograph of a cell from an insect testis. The cell is in anaphase. The chromosomes appear as V-shaped structures moving towards opposite poles, with some chromosomes clearly consisting of…
  22. Describe5 marksStandardA non-consanguineous couple, both with normal pigmentation, have a child with oculocutaneous albinism (lack of melanin in skin, hair and eyes). Genetic analysis shows that the child is homozygous recessive for a…
  23. Describe4 marksStandardThe diploid chromosome number of a species is 8. Describe the events that take place during prophase I and metaphase I of meiosis in a cell of this species.
  24. Determine5 marksStandardIn humans, the TYR gene codes for the enzyme tyrosinase, which is involved in melanin production. Albinism is an autosomal recessive condition resulting from a non-functional tyrosinase. A man and a woman, both with…
  25. Explain5 marksStandardIn a bacterium, the malX operon consists of a regulatory gene, malR, and three structural genes: malA, malB, and malC. The malR gene codes for a repressor protein. In the absence of maltose, the repressor binds to the…
  26. Describe4 marksStandardA farmer crossed a pea plant that was heterozygous for two genes, A and B (genotype AaBb), with a plant that was homozygous recessive for both genes (aabb). The offspring phenotypes and their numbers are shown in the…
  27. Describe5 marksStandardDescribe the differences between structural genes and regulatory genes, and between inducible and repressible enzymes, using the lac operon as an example of an inducible system. Present your answer as a table comparing…
  28. Explain5 marksStandardIn a diploid organism with two pairs of homologous chromosomes (2n = 4), explain how independent assortment during meiosis results in the production of genetically different gametes.
  29. Determine4 marksStandardIn a plant species, flower colour is controlled by two unlinked genes, A and B. Gene A controls pigment production: the dominant allele A allows pigment production, while the recessive allele a prevents pigment…
  30. Explain4 marksStandardIn a species of plant, flower colour is determined by a single gene with two codominant alleles. The allele C^R produces red flowers, and the allele C^W produces white flowers. Plants with genotype C^R C^W have pink…
  31. Describe5 marksStandardA species of butterfly has a diploid chromosome number of 40 (2n = 40). Describe why a reduction division (meiosis) is necessary before fertilisation in the life cycle of this butterfly. In your answer, explain the…
  32. Explain5 marksStandardA couple, both heterozygous for the sickle cell allele (HbA HbS), are planning to have children. The allele for normal haemoglobin (HbA) and the allele for sickle haemoglobin (HbS) show codominance. Explain the…
  33. Outline5 marksStandardTable 1 shows the relative activity of β-galactosidase in cultures of E. coli grown in the presence and absence of lactose. Growth condition Relative β-galactosidase activity without lactose 0 with lactose 100 Outline…
  34. Describe6 marksChallengeIn a species of plant, flower colour is determined by two unlinked genes, A and B. Alleles: A (dominant) and a (recessive); B (dominant) and b (recessive). A cross between two plants, both heterozygous at both loci…
  35. Describe5 marksChallengeA student studying meiosis in a locust testis recorded the following descriptions of four cells at different stages. (Note: The descriptions are not in chronological order.) Cell P: Condensed chromosomes are visible as…
  36. Outline7 marksChallengeA scientist is investigating a dwarf pea mutant 'na' that overproduces DELLA protein. Normal pea plants grow tall when treated with gibberellin (GA), but the mutant remains dwarf even after GA treatment. (a) Outline…
  37. Explain5 marksChallengeIn the bacterium Escherichia coli, the lac operon controls the production of enzymes needed for lactose metabolism. In plants, the hormone gibberellin stimulates seed germination by activating the expression of genes…
  38. Describe6 marksChallengeGibberellin (GA) is a plant hormone that promotes seed germination by activating transcription of the α-amylase gene. In the absence of GA, a DELLA protein binds to a transcription factor, preventing it from…
  39. Explain6 marksChallengeA species of plant has a diploid chromosome number of 8 (2n = 8). Explain why the number of genetically different gametes that a single individual of this species can produce is far greater than the number predicted by…
  40. Outline7 marksChallengeThe table below shows the relative activity of β-galactosidase in a bacterial strain grown under two conditions. Growth condition β-galactosidase activity (arbitrary units) Without lactose 2 With lactose 100 Outline…
  41. Describe6 marksChallengeIn humans, the allele for normal haemoglobin (HbA) is dominant over the allele for sickle cell haemoglobin (HbS). A man who is heterozygous for the sickle cell trait and a woman who is also heterozygous plan to have…
  42. Explain5 marksChallengeA woman who is a carrier for haemophilia (genotype X^H X^h) and a man with haemophilia (X^h Y) have ten children. The observed numbers, determined by DNA analysis, are: Normal male (blood clotting normal): 1…
  43. Determine7 marksChallengeIn a species of insect, body colour (grey or black) and wing shape (normal or vestigial) are controlled by two autosomal genes. A grey-bodied, normal-winged insect that is heterozygous for both genes is test-crossed…
  44. Describe6 marksChallengeA plant gene that codes for an enzyme involved in cell elongation is regulated by the hormone gibberellin. The transcription factor that activates this gene is normally kept inactive by binding to a DELLA protein…
  45. Describe6 marksChallengeDescribe the differences between structural genes and regulatory genes, and between repressible and inducible enzymes. Use the lac operon in E. coli to illustrate the control of protein production by an inducible…
  46. Explain6 marksChallengeA diploid plant species has a chromosome number of 2n=4. A particular plant is heterozygous for three genes: gene A (alleles A and a), gene B (alleles B and b), and gene C (alleles C and c). Genes A and B are located…
  47. Describe6 marksChallengeSickle cell anaemia is caused by a mutation in the HBB gene, which codes for the beta-globin polypeptide of haemoglobin. The normal allele is HbA and the mutant allele is HbS. Individuals who are homozygous for HbS…
  48. Explain6 marksChallengeA diploid plant cell (2n = 4) contains two pairs of homologous chromosomes: one long pair (L1 and L2) and one short pair (S1 and S2). The L chromosomes carry the allele A or a, and the S chromosomes carry the allele B…
  49. Describe6 marksChallengeDescribe the differences between inducible and repressible enzyme systems in the control of gene expression. In your answer you should include: the roles of structural genes and regulatory genes the mechanism of the…
  50. Determine7 marksChallengeIn a species of beetle, wing length and antenna colour are controlled by two autosomal genes. Long wings (L) are dominant over short wings (l), and black antennae (B) are dominant over brown antennae (b). A test cross…
  51. Explain5 marksChallengeIn humans, pigmentation is controlled by the TYR gene. The TYR gene codes for the enzyme tyrosinase, which catalyses the production of melanin. Albinism is a condition characterised by a lack of melanin in the skin…
  52. Outline7 marksChallengeA species of butterfly, Vanessa cardui, has a diploid chromosome number of 2n = 20. Outline how the processes of meiosis and fertilisation generate genetic variation in the offspring of this butterfly. Your answer…
  53. Explain5 marksChallengeUsing the lac operon in Escherichia coli and gibberellin-induced gene activation in plants as examples, explain the distinction between structural genes and regulatory genes, and describe how regulatory gene products…
  54. Outline7 marksChallengeA student prepared microscope slides of cells from a plant with a diploid chromosome number of 8 (2n = 8). Two cells undergoing meiosis are observed. Cell X: Chromosomes are moving towards opposite poles. Each…
  55. Describe5 marksChallengeA species of orchid has a diploid chromosome number of 12 (2n = 12). Describe the key events that occur during meiosis in the cells of this orchid that lead to the formation of haploid gametes, and explain why a…
  56. Determine7 marksChallengeA plant breeder crossed a homozygous purple-flowered, hairy-stemmed plant (genotype PPHH) with a homozygous white-flowered, smooth-stemmed plant (pphh). The purple flower allele (P) is dominant to white (p), and hairy…
  57. Outline7 marksChallengeIn prokaryotes, the lac operon controls the production of enzymes for lactose metabolism. In eukaryotes, plant stem elongation is promoted by gibberellin, which acts by causing breakdown of DELLA repressor proteins…
  58. Describe6 marksChallengeIn a species of tropical fish, fin colour is controlled by a single gene with two codominant alleles: C^R (red) and C^W (white). Fish that are homozygous for C^R have red fins, those homozygous for C^W have white fins…
  59. Explain6 marksChallengeA plant cell is heterozygous for three genes: T and t (tall/short stems) and L and l (large/small leaves) are linked on the same chromosome pair. F and f (fragrant/non-fragrant flowers) are on a different chromosome…
  60. Outline7 marksChallengeA photomicrograph shows a cell from a grasshopper testis during meiosis. The original parent cell has a diploid number of 12 (2n = 12). In the photomicrograph, chromosomes are moving towards opposite poles. Each…