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Q25 - beta-catenin and GSK3beta in Xenopus Dorsal Organizer Formation

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

In a Xenopus embryo, the dorsal-ventral axis is determined through cortical rotation after fertilization. On the dorsal side of an embryo, the Spemann-Mangold organizer is necessary to determine the body plan of the embryo. When the organizer formation is inhibited, a head defect occurs in embryos. On the other hand, the head is enlarged when the organizer region expands. beta-catenin (beta-cat) and GSK3beta are involved in organizer formation. The table below shows the results of phenotype of tadpoles microinjected with beta-cat, GSK3beta, and beta-cat (beta-catenin inhibition factor), and DN GSK3beta (GSK3beta inhibition factor) into the dorsal or ventral side of the embryo.

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

A. This experiment shows that GSK3beta inhibited organizer formation.
B. This experiment shows that GSK3beta inhibits beta-cat activity.
C. This experiment shows that beta-cat is not expressed in ventral region.
D. This experiment shows that GSK3beta works downstream of beta-cat.
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Question reproduced from IBO 2020, Theoretical Exam 1, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)