Q1 - Neurospora Pathway Reconstruction

Theoretical 1 Real exam question - full text reproduced under IBO's CC BY-NC-SA 4.0 license

Gene Interactions: Epistasis & Complementation Analysis

Compounds X and Y are precursors in the pathway of Z synthesis. Z is essential for growth. Wild type (WT) Neurospora are prototrophs, meaning that they can grow on minimal medium (MM). Growth Experiment: Four Z- neurospora mutants were isolated, and results of experiments with these mutants are presented below (+ = growth, − = no growth). Complementation Tests: Complementation tests were performed by testing for growth of heterokaryons in minimal medium. Results were as follows (+ = growth, − = no growth). Mating Experiment: Mutant strains were mated and % prototrophs among spores of each mating were determined. Results were as follows.

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

A. The mutations in the mutated strains were distributed in two genes.

B. Considering all the mutant strains, at least five different sites of the Neurospora genome were mutated in one or more strains.

C. At least two of the mutant strains were double mutants (i.e. > 1 site was mutated in each of these strains).

D. The mutation site of Mutant 3 is positioned between the mutation site in Mutant 2 and the mutation site in Mutant 4.

E. It is expected that 25% of spores resulting from mating between Mutant 2 and wild type strain will be prototrophs.

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Question reproduced from IBO 2018, Theoretical Paper 1, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)