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You are a scientist at the CDC studying pathogen evolution in response to antibi

ID: 151764 • Letter: Y

Question

You are a scientist at the CDC studying pathogen evolution in response to antibiotics. You have two flasks of C. elegans in the lab. You are studying one locus, wherein the R allele confers resistance to drug R, but allele r does not. You are also studying a second locus, wherein the P allele confers resistance to drug P, but allele p does not. In Flask 1 the frequency of the R allele is 0.6, the frequency of the P allele is 0.4, and the fully resistant RP haplotype frequency is 0.24. In Flask 2 the R allele frequency is 0.3, the P allele frequency is 0.1, and the fully resistant RP haplotype frequency is 0.04.

a) In which flask is there evidence of linkage disequilibrium between the two loci?

b) True/False: For Flask 1, exposure to drug R, and thus selection favoring the R allele, would result in linkage disequilibirum between the two loci

c) True/False. For Flask 2, exposure to drug P, and thus selection favoring the P allele, would alter evolution at the locus controlling resistance to drug R.

Explanation / Answer

(a) In flask 1, there is evidence of linkage between R and P A’s frequency of RP haplotype is more in flask 1.

(b) True, as exposure to drug R would result in increased drug resistant variant or R allele frequency and further leading to linkage disequilibrium.

(c) True, as the environmental conditions are changed for the locus controlling resistance to drug R that would lead to alteration in evolution.