A Strain of Yeast Translates MRNA into Protein Inaccurately Figure 7-33

A strain of yeast translates mRNA into protein inaccurately.Individual molecules of a particular protein isolated from this yeast have variations in the first 11 amino acids compared with the sequence of the same protein isolated from normal yeast cells, as listed in Figure 7-33.What is the most likely cause of this variation in protein sequence? $\begin{array}{c}\begin{array}{lll}\text {normal sequence}\\\\\text {variants}\\\\\\\\\\\\\end{array}\begin{array}{lll} \text {Met}\\\\ \text {Met}\\ \text {Met}\\ \text {Met}\\ \text {Met}\\ \text {Met}\\ \text {Met}\end{array}\begin{array}{lll} \text {Thr}\\\\ \text {Thr}\\ \text {Thr}\\ \text {Thr}\\ \text {Thr}\\ \text {Thr}\\ \text {Thr}\end{array}\begin{array}{lll} \text {Ala}\\\\ \text {Ala}\\ \text {Ala}\\ \text {Ala}\\ \text {Ala}\\ \text {Ala}\\ \text {Ala} \end{array}\begin{array}{lll} \text {Ile}\\\\ \text {Ala}\\ \text {Gly}\\ \text {val}\\ \text {Ile}\\ \text {Ile}\\ \text {Ile} \end{array}\begin{array}{lll} \text {Val}\\\\ \text {Val}\\ \text {Val}\\ \text {Val}\\ \text {Val}\\ \text {Val} \\ \text {Va} \end{array}\begin{array}{lll}\text {Ser}\\\\\text {Ser}\\\text {Ser}\\\text {Ser}\\\text {Ser}\\\text {Ser}\\\text {Ser}\end{array}\begin{array}{lll}\text {Asn}\\\\\text {Asn}\\\text {Asn}\\\text {Asn}\\\text {Asn}\\\text {Asn}\\\text {Asn}\end{array}\begin{array}{lll}\text {Thr}\\\\\text {Thr}\\\text {Thr}\\\text {Thr}\\\text {Thr}\\\text {Thr}\\\text {Thr}\end{array}\begin{array}{lll}\text { Gln}\\\\\text { Gln } \\\text { Gln } \\\text { Gln } \\\text { Gln } \\\text { Gln } \\\text { Gln }\end{array}\begin{array}{lll}\text { Ile}\\\\\text { Ile}\\\text { Ile}\\\text { Ile}\\\text { Ala}\\\text { Gly}\\\text { Val}\end{array}\begin{array}{lll}\text {Lys}\\\\\text {Lys}\\\text {Lys}\\\text {Lys}\\\text {Lys}\\\text {Lys}\\\text {Lys}\\\end{array}\end{array}$
Figure 7-33 $\text { The Genetic Code }$
$\begin{array}{|l|l|l|l|l|}\hline & \text { U } & \text { C } & \text { A } & \text { G } \\\hline &\text { UUU Phe (F) } & \text { UCU Ser (S) } & \text { UAU Tyr (Y) } & \text { UGU Cys (C) } \\&\text { UUC - } & \text { UCC - } & \text { UAC - } & \text { UGC - } \\ \text { U } &\text { UUA Leu (L) } & \text { UCA -- } & \text { UAA Stop } & \text { UGA Stop } \\&\text { UUG - } & \text { UCG - } & \text { UAG Stop } & \text { UGG Trp (W) } \\\hline &\text { CUU Leu (L) } & \text { CCU Pro (P) } & \text { CAU His (H) } & \text { CGU Arg (R) } \\&\text { CUC - } & \text { CCC - } & \text { CAC - } & \text { CGC - } \\ \text { C}&\text { CUA - } & \text { CCA - } & \text { CAA Gin (Q) } & \text { CGA - } \\&\text { CUG }- & \text { CCG }- & \text { CAG }- & \text { CGG }- \\\hline &\text { AUU Ile (I) } & \text { ACU Thr (T) } & \text { AAU Asn (N) } & \text { AGU Ser (S) } \\&\text { AUC - } & \text { ACC - } & \text { AAC - } & \text { AGC - } \\ \text { A}&\text { AUA - } & \text { ACA - } & \text { AAA Lys (K) } & \text { AGA Arg (R) } \\&\text { AUG Met (M) } & \text { ACG - } & \text { AAG - } & \text { AGG - } \\\hline &\text { GUU Val (V) } & \text { GCU Ala (A) } & \text { GAU Asp (D) } & \text { GGU Gly (G) } \\&\text { GUC - } & \text { GCC - } & \text { GAC - } & \text { GGC - } \\ \text { G}&\text { GUA - } & \text { GCA - } & \text { GAA Glu (E) } & \text { GGA - } \\&\text { GUG - } & \text { GCG - } & \text { GAG - } & \text { GGG - } \\\hline\end{array}$

Table 7-29

A) a mutation in the DNA coding for the protein
B) a mutation in the anticodon of the isoleucine-tRNA (tRNA^Ile)
C) a mutation in the isoleucyl-tRNA synthetase that decreases its ability to distinguish between different amino acids
D) a mutation in the isoleucyl-tRNA synthetase that decreases its ability to distinguish between different tRNA molecules