Q39 - Identifying Unlabeled Cetartiodactyl DNA Samples from a Phylogenetic Sequence Alignment

Theoretical 2 Real exam question - full text reproduced under IBO's CC BY-NC-SA 4.0 license

Molecular Systematics Evidence for Evolution

A laboratory found three tubes lacking labels among stored mammal DNA samples, with three removed labels found nearby: “bowhead whale”, “pigmy hippopotamus” and “water buffalo”. A fourth tube in the same shelf was labeled “bottlenose dolphin”. A specific genomic region was sequenced from the DNA of the three label-less tubes (#2, #3, #4) and the bottlenose dolphin (#1), assuming this region evolves under a constant rate among cetartiodactyls. The known phylogenetic relationship of the four species is: bottlenose dolphin and bowhead whale are close relatives (both cetaceans), sharing a more distant common ancestor with the pygmy hippopotamus, and water buffalo is the outgroup to all three.

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

tube-to-label match. Based on the sequence alignment and known phylogenetic relationships, indicate the most likely combination of tubes and labels for tube #2, #3, and #4.

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Question reproduced from IBO 2020, Theoretical Exam 2, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)