Exam 4 Practice Problems Key

Exam 4 Practice Problems Key - Biology 471 Practice Problem...

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Biology 471 Practice Problem for Exam 4 1. The following is a small portion of the gene coding for 6-phosphogluconate dehyrogenase in two natural isolates of E. coli. 1 CTG ACC AAA ATC GCC GCC GTA GCT GAA GAC GGT GAA CCA TGC GTT ACC TAT ATT GGT GCC 2 CTG AAG CAG ATC GCG GCG GTT GCT GAA GAC GGT GAG CCG TGT GTG ACT TAT ATA GGT GCC Spacing between codons indicates the correct translational reading frame. Assume that mutations in codon positions 1 and 2 produce non-synonymous changes, and that mutations in codon position 3 produces a synonymous change). From these sequences, estimate: a. The number of amino acid differences/site. 2 differences/20 amino acid sites = .1 b. The number of nucleotide differences/site. 13/60 nucleotide sites c. The number of nonsynonymous substitutions per nonsynonymous site (dN). 2/40 = .05 d. The number of synonymous substitutions per synonymous site (dS). 11/20 = .55 e. dN/dS .05/.55 = .091 f. What can you infer about the way selection is acting on this gene? dN/dS is much smaller than 1, therefore most amino acid changes are deleterious, and selection is
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This note was uploaded on 05/01/2008 for the course BIOL 471 taught by Professor Burch during the Spring '08 term at UNC.

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Exam 4 Practice Problems Key - Biology 471 Practice Problem...

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