Q38 - Parsimony Reconstruction of Opsin Gene Evolution in Human and Zebrafish

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

Following is the phylogenetic tree based on the amino-acid sequences of all opsin genes in the human and zebrafish genomes. Indicate whether each of the following statements is true or false under a parsimony principle.

A phylogenetic tree based on the amino-acid sequences of all opsin genes in the human and zebrafish genomes. LWS: Long Wavelength Sensitive opsin, MWS: Middle Wavelength Sensitive opsin, SWS: Short Wavelength Sensitive opsin, UVS: Ultra Violet Sensitive opsin, RH: Rhodopsin type opsin. A phylogenetic tree based on the amino-acid sequences of all opsin genes in the human and zebrafish genomes. LWS: Long Wavelength Sensitive opsin, MWS: Middle Wavelength Sensitive opsin, SWS: Short Wavelength Sensitive opsin, UVS: Ultra Violet Sensitive opsin, RH: Rhodopsin type opsin.

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

A. In the phylogenetic tree, zebrafish SWS is most closely related to RH.

B. The common ancestor of the human and zebrafish had four opsin genes in the genome.

C. The opsin gene at node I was supposed to encode an LWS.

D. The zebrafish has acquired five opsin genes after splitting from the human.

E. The human has lost two opsin genes after splitting from the zebrafish.

F. The common ancestor of the human and zebrafish did not have any SWS in the genome.

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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)