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(Solved): 7. You are studying a gene in E. coli that codes for a protein. A part of its sequence is: - Ala - ...
7. You are studying a gene in E. coli that codes for a protein. A part of its sequence is: - Ala - Pro - Jor- Ue- Gar Lys - Cue-His - You recover a series of mutants for this gene that show no enzymatic activity. By isolating the mutant enzyme products, you find the following protein sequences: Mutant 1: - Ala - Pro - Mutant 2: - Ala - Pro - JRa Lys - GlP - Lys - Grs - His - Mutant 3: - Ala - Pro - Gbr- Jwe-Arg - Ses- Ala - Met - a. Compare Mutant 1 to the normal protein. What spccific point mutation (show nucleotides in mRNA) oceurred to the codon that encoded IrR for this to occur? Consult the codon table. b. Compare Mutant 2 to the normal protein. What snecific point mutation (show nucleotides in mRNA) occurred to cause the lle to become Lys? c. Challenge question: Compare Mutant 3 to the normal protein. ONE point mutation occurred to cause the mutant protein. Identify the specific point mutation.
a. Compare mutant 1 to the normal protien.The normal protein sequence is -Ala-Pro-Thr-Val-Lys-His-.The mutant 1 sequence is Ala-Pro-. Thus, the mutant 1 has lost two amino acids (Thr and Val) at the C-terminal end of the protein. The codon table shows that the codon for Ala is GCU, GCC, GCA, or GCG, and the codon for Pro is CCU, CCC, CCA, or CCG. Therefore, the codon for the LR dipeptide that was deleted in the mutant 1 should have been ACU, ACC, ACA, or ACG. The deletion could have occurred by a frameshift mutation caused by the insertion or deletion of a nucleotide within this codon.