You are studying the tryptophan synthetase gene that Yanofsky also examined to determine the relationship between the nucleotide sequence and the amino acid sequence of the gene. Yanofsky found a large number of mutations that affected the tryptophan synthetase gene. A) If you took this mutant E. Coli line (that has an Arginine at this location) and exposed it to a mutagen that could potentially change bases, what are the second mutations you would most likely discover that would restore the activity of the tryptophan synthetase gene and where would it be located? B) Most of the mutations that Yanofsky recovered were missense mutations. However, Yanofsky also recovered a nonsense mutation that changed amino acid number 15 into a stop codon. This codon normally encodes Lysine. Does the recovery of this mutation support the hypothesis that this Lysine residue is critical in the function of the tryptophan synthetase protein?

Human Heredity: Principles and Issues (MindTap Course List)
11th Edition
ISBN:9781305251052
Author:Michael Cummings
Publisher:Michael Cummings
Chapter9: Gene Expression And Gene Regulation
Section: Chapter Questions
Problem 15QP
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You are studying the tryptophan synthetase gene that Yanofsky also examined to determine the relationship between the nucleotide sequence and the amino acid sequence of the gene. Yanofsky found a large number of mutations that affected the tryptophan synthetase gene.

A) If you took this mutant E. Coli line (that has an Arginine at this location) and exposed it to a mutagen that could potentially change bases, what are the second mutations you would most likely discover that would restore the activity of the tryptophan synthetase gene and where would it be located?

B) Most of the mutations that Yanofsky recovered were missense mutations. However, Yanofsky also recovered a nonsense mutation that changed amino acid number 15 into a stop codon. This codon normally encodes Lysine. Does the recovery of this mutation support the hypothesis that this Lysine residue is critical in the function of the tryptophan synthetase protein?

Gene and protein are colinear
Yanofsky (1964)
Gene
Positions of
mutations
Protein
+H3N
C-
49
175 177 183
211
213
1.
Gly
1
15 22
234
235 243 268
Wild-type
amino acids
Lys Phe
Glu
Tyr Leu Thr
Gly
Gly
Ser Gin
Stop Leu Val Gin Met
Altered
amino acids
Cys Arg lle Arg Glu Val Cys Asp Leu Stop
Transcribed Image Text:Gene and protein are colinear Yanofsky (1964) Gene Positions of mutations Protein +H3N C- 49 175 177 183 211 213 1. Gly 1 15 22 234 235 243 268 Wild-type amino acids Lys Phe Glu Tyr Leu Thr Gly Gly Ser Gin Stop Leu Val Gin Met Altered amino acids Cys Arg lle Arg Glu Val Cys Asp Leu Stop
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