Gene expression and cancerAQA A-Level Biology: Subtopic test

1. 1
   A surgeon removes lumps from two different patients. Lump A grew slowly, was surrounded by a capsule and contained cells that looked similar to normal cells. Lump B grew rapidly, had no capsule and contained cells with large dark nuclei and very different sizes. Cells identical to those in lump B were later found in nearby lymph nodes.

   (a)

   Which description fits lump A as a benign tumour?

   [1 mark]

   • AIt is surrounded by a capsule and does not spread to other tissues
   • BIts cells spread to form secondary tumours
   • CIt grows rapidly
   • DIts cells have large nuclei of very different sizes

   (b)

   What best explains why cells identical to lump B were found in the lymph nodes?

   [1 mark]

   • AApoptosis of the tumour cells
   • BDifferentiation of normal lymph node cells
   • CMetastasis of cells from the tumour
   • DMethylation of the DNA in lymph node cells

   (c)

   Explain why lump B is more life-threatening than lump A.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   Cell division in a tissue is controlled by two genes. The protein from gene X stimulates cells to divide. The protein from gene Y slows cell division and can cause a damaged cell to die. In tumour 1 the gene X protein was active all the time. In tumour 2 the promoter region of gene Y was heavily methylated.

   (a)

   What term describes the mutated form of gene X that is active all the time?

   [1 mark]

   • ATumour suppressor gene
   • BProto-oncogene
   • CRegulator gene
   • DOncogene

   (b)

   What is the effect of the methylation of the promoter region of gene Y in tumour 2?

   [1 mark]

   • AGene Y is transcribed more often
   • BGene Y is not transcribed, so the protein that slows cell division is not made
   • CThe base sequence of gene Y is changed
   • DThe protein from gene Y is active all the time

   (c)

   Explain how the changes in tumour 1 and tumour 2 could each lead to uncontrolled cell division.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Some breast cancers grow faster when the concentration of oestrogen is high. The cells of these tumours have oestrogen receptors. Researchers have designed a drug with a shape similar to oestrogen that binds to the receptor but does not activate it.

   (a)

   Explain how an increased concentration of oestrogen can contribute to the development of some breast cancers.

   [3 marks]

   (b)

   Explain how the drug could slow the growth of these tumours, and why it would be ineffective for a tumour whose cells lack oestrogen receptors.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Women who carry a mutated allele of the tumour suppressor gene BRCA1 have about a 70% chance of developing breast cancer by the age of 80, compared with about 12% for women who do not carry it. Among carriers, women born after 1950 had a higher risk than those born before 1920. In women without the mutation, regular heavy alcohol consumption was linked to a higher risk. Only about 5% of all breast cancers occur in women who carry the mutation.

   (a)

   Evaluate the evidence for the roles of genetic and environmental factors in the development of breast cancer.

   [6 marks]

   (b)

   Interpret how an understanding of the roles of oncogenes and tumour suppressor genes could be used in the prevention, treatment and cure of cancer.

   [6 marks]

   Total for question 4: 12 marks

End of questions