Skip to content
← Theoretical 2

Q37 - Tracking Hox Cluster and Gene Duplication History Through Vertebrate Phylogeny

Theoretical 2 Real exam question - full text reproduced under IBO's CC BY-NC-SA 4.0 license
Chromosomal Variation: Number & Structure Molecular Systematics

During the evolutionary history of vertebrates, they experienced several instances of whole-genome duplication that are believed to facilitate genome diversification and dynamic evolution. A. Figure 1 shows the phylogenetic tree of a broad range of vertebrates and lancelet (an ancestor of vertebrates) with the timing of whole-genome duplications (black arrowheads) marked on the tree. The lancelet possesses one Hox gene cluster in the genome, and Hox gene clusters are rarely lost during evolution. B. In the phylogenetic tree of species X, Y, and Z, whole-genome duplication occurred two times (black arrowheads, Figure 2 left), so each of species X, Y, and Z possesses two paralogous genes (X1/X2, Y1/Y2, Z1/Z2). Enough time has passed between gene duplication and the subsequent speciation.

(left) The phylogenetic tree of a broad range of vertebrates and lancelet (an ancestor of vertebrates). (right) The answer options for the number of Hox gene clusters in each species from (1) to (6). (left) The phylogenetic tree of a broad range of vertebrates and lancelet (an ancestor of vertebrates). (right) The answer options for the number of Hox gene clusters in each species from (1) to (6).

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

A. Choose the appropriate combination of the numbers of Hox gene clusters (observed) in vertebrates from the answer options given in Figure 1.
B. Choose the appropriate phylogenetic tree of the genes X1 to Z2 (from the answer options given in Figure 2) for species X, Y, and Z, given that two rounds of whole-genome duplication occurred as shown.
← Previous: Q36 Next: Q38 →

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)