Skip to content
📢We are still a growing community and would love some help. Want to contribute? Join us by mailing an e-mail of interest to "r6394175@gmail.com"
Start helping our community →
← Theoretical 1

Q41 — Angelman Syndrome — Genomic Imprinting Pedigree

Theoretical 1 Real exam question — full text reproduced under IBO's CC BY-NC-SA 4.0 license
Pedigree Analysis & Human Genetic Disorders Extranuclear & Non-Mendelian Inheritance

Angelman Syndrome (AS) is caused by a mutation of the ube3a gene. Affected individuals display delayed development, impaired cognitive abilities, and frequent laughter for no apparent reason. The following pedigree describes the inheritance pattern in a family of carriers; the mutation is rare enough that no carrier married another carrier. All individuals labeled white are phenotypically healthy.

Four-generation pedigree tracking UBE3A mutation carriers and Angelman syndrome cases. Pedigree of a family with Angelman Syndrome. Dot = UBE3A mutation carrier; filled teal shape = individual with Angelman syndrome.

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

A. This mutation is recessive and is on an autosomal chromosome.
B. Mendelian inheritance is insufficient to explain the inheritance of AS.
C. If II-3 has a third child, then the child will surely have AS, just like II-3's other two children.
D. If individual III-1 conceived a child with a non-carrier woman, their progeny would have a 50% chance of having AS.
← Previous: Q40 Next: Q42 →

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)