Q20 — Haploid/Diploid Organisms and Multi-Allele Genetics

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

Imagine a planet inhabited by animal-like creatures capable of both meiosis and mitosis, where the fundamental principles of genetics apply. This species is distinguished by two alternating heteromorphic generations: haploid and diploid.

The haploid (n) generation consists of intelligent beings who dwell in urban environments and form pairs of sexual partners. In contrast, individuals of the diploid (2n) generation are non-rational and aggressive and are reared in specialized nurseries. The haploid pairs entrust their offspring to these nurseries, where the diploid organisms give rise to a new haploid generation.

In one locus of these organisms, there are three alleles: A1 (most dominant) > A2 > A3 (most recessive). Among the 2n generation, 1% of organisms have the A3 phenotype, 8% have the A2 phenotype, and 91% have the A1 phenotype. The entire population is in genetic equilibrium.

On your answer sheet, indicate “T” for true statements and “F” for false ones.

A. Individuals with the A1 phenotype make up more than 75% of the haploid generation.

B. There are two possible genotypes for individuals with the A2 phenotype in the 2n generation

C. Each haploid organism has one "grandfather" and one "grandmother", from each of which it has exactly 50% of its genetic material.

D. When a recessive lethal mutation that blocks mitosis occurs in this gene, it can persist in the population for many generations.

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Question reproduced from IBO 2024, Theoretical Exam Part A, licensed under CC BY-NC-SA 4.0 — attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)