Q39 - Synonymous vs Non-Synonymous Variation in Humans

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

Bustamante et al. (2005) analysed the pattern of polymorphism in the human genome by sequencing over 11,624 genes from 39 humans. The table below shows the distributions of synonymous (changes that does not result in amino acid replacement) and non-synonymous (changes that result in amino acid replacement) single nucleotide polymorphism (SNPs - variation within species): In the table, divergence refers to the fixed differences between the humans in this study and the chimpanzee genome.

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

A. Greater ratio of non-synonymous to synonymous SNPs relative to ratio of non-synonymous to synonymous divergent sites suggest the effect of negative selection in human.

B. The ratio of synonymous/non-synonymous SNPs is higher in genes involved in chromatin structure.

C. Arms races caused by host-specific pathogen would decrease the ratio of synonymous/non-synonymous substitutions in divergent sites between human and chimpanzee.

D. SNPs present within chimpanzee population cannot result in any level of reproductive isolation in chimpanzee population.

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Question reproduced from IBO 2018, 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)