Q37 - Gene Duplication and Selection in Primate ECP/EDN Ribonuclease Genes

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

The following figure is a phylogenetic tree of ECP and EDN genes in primates. EDN shows strong ribonuclease activity. By contrast, ECP shows strong anti-bacterial function, although its ribonuclease activity is weak.

A molecular phylogenetic tree of ECP and EDN genes in primates based on amino-acid sequences. The numerator and denominator along each branch show the numbers of nonsynonymous and synonymous nucleotide substitutions (substitutions that cause and do not cause amino-acid changes), respectively. A molecular phylogenetic tree of ECP and EDN genes in primates based on amino-acid sequences. The numerator and denominator along each branch show the numbers of nonsynonymous and synonymous nucleotide substitutions (substitutions that cause and do not cause amino-acid changes), respectively.

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

A. The most recent common ancestor of these primate species only had the EDN gene.

B. It is likely that the Human, Chimpanzee, Gorilla, Orangutan, and Macaque independently obtained the ECP gene by gene duplication.

C. The number of synonymous substitutions in branches between common ancestor X and human ECP is smaller than that between X and human EDN.

D. During the early evolution of the ECP gene, positive selection likely operated on mutations that enhance anti-bacterial activity.

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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)