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Q34 - p53's Tetramer Threshold Guards Against Cancer

Theoretical B Real exam question - full text reproduced under IBO's CC BY-NC-SA 4.0 license
Cell Cycle, Mitosis & Meiosis

The major ways by which the cell-cycle is regulated in all eukaryotes were discovered by British scientists. In humans, Cyclins (discovered by Sir Tim Hunt; 1943-present) are transcribed at specific cell-cycle stages, and bind cyclin-dependent kinases (CDK; discovered by Sir Paul Nurse; 1949-present), to coordinate division. Protein-53 (p53; discovered by Sir David Lane; 1952-present) is activated by a huge array of post-translational modifications, which allows it to exert diverse effects. p53 can exert these effects even when its activity is reduced by half, but each p53 monomer is only active when bound to three other functional p53 monomers in a homotetramer. p53 is mutated in the majority of cancers ever sequenced.

Figure 1 for Q34: p53’s Tetramer Threshold Guards Against Cancer

Using the information and data, determine which of the statements are true or which are false.

A. Tumours which have lost p53 activity have higher mutation rates than tumours which have p53 activity.
B. Single celled organisms, such as yeast (Saccharomyces), possess equally powerful regulators like p53.
C. Treatments which deliver more p53 to cells, would reduce the division of healthy cells.
D. Both alleles of p53 are usually mutated in cancer.
E. P53 knockout mice (Mus musculus) show an overgrowth of bone-marrow cells.
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Question reproduced from IBO 2017, Theoretical Exam B, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Official answer key & worked solutions