Q29 - Random Sorting of Chloroplasts in a Variegated Plant

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

Extranuclear & Non-Mendelian Inheritance

Four o’clock plants (Mirabilis jalapa) can have a mix of white and green patches on their leaves, so they appear variegated - a picture showing the different colours of branches possible, but not necessarily the usual pattern of these branches, is shown (1). Variegated plants were grown, and flowers on green, white or variegated branches were fertilised by pollen from green, white or variegated branches. The progeny had the following phenotypes. Phenotype of branch bearing seed Phenotype of branch bearing pollen Phenotype of offspring plant White White White White Green White White Variegated White Green White Green Green Green Green Green Variegated Green Variegated White White, green, or variegated Variegated Green White, green, or variegated Variegated Variegated White, green, or variegated

Figure 1 for Q29: Random Sorting of Chloroplasts in a Variegated Plant

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

A. Chloroplasts can be transmitted through pollen during Four o’clock plant reproduction.

B. During cell division as a plant grows, each daughter cell has the same composition of alleles.

C. Egg cells in a variegated flower can contain different chloroplasts with distinct genomes.

D. Older branches of a variegated four o’clock plant are more likely to be all white, or all green, than younger branches.

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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