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← Theoretical 1

Q32 — Shiverer Mutation — Optic Nerve Myelin

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

The shiverer mutation is known to affect the Central Nervous System (CNS), causing tremors and early death in mice. To investigate its effects, the optic nerve — which, unlike all other nerves, is histologically equivalent to the CNS — was cut transverse and stained for lipids (A – wild type, B – mutant).

Cross-sections of wild-type (A) and shiverer-mutant (B) optic nerve, stained for lipids. Transverse optic nerve cross-sections stained for lipids: A — wild type, B — shiverer mutant.

Using the information and image, determine whether the following statements are true or false:

A. Picture A contains multiple Schwann cells.
B. Ion channels of neurons in Picture B were directly affected by the mutation.
C. The shiverer mutation severely compromises oligodendrocytes.
D. In Picture A we could see the nucleus in place of the asterisk, if we stained the sample with DAPI.

Question reproduced from IBO 2022, 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)