M201PS6Answers2008 - MICB 201 Chapter 6 Answers Problem#1...

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MICB 201 Chapter 6 Answers Problem #1 OMIT Problem #2 The mutation results in a new mRNA codon that specifies the same amino acid as before, eg. Wild-type Mutant DNA 5’-TTT-3’ 5’-TTC-3’ 3’-AAA-5’ 3’-AAG-5’ RNA 5’-UUU-3’ 5’-UUC-3’ Amino acid Phe Phe Problem #3 (Done in class) As discussed in class, by the time the population has grown from 1 cell to128 cells (between 6-7 generations) one would expect to find one cell in the population with a spontaneous base substitution mutation somewhere in the chromosome. Problem #4 2.5 x 10 -17 Problem #5 (a) N-Met-Pro-Ala-Cys-Asp-Val-Gly-Phe-Leu-C (b) Gly to Asp (c) Leu to Arg (d) Mutant protein has amino acid sequence: N-Met-Pro-Gly-Met-C
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Problem #6 (a) Deletion of one nucleotide pair in DNA causes translation of the nucleotides in mRNA by the ribosome to be shifted to different groups of three, eg DNA 3’-TAC-GAT-GAT-CGA-ATG-GAT-AAG-CTA-AGA-TGG-ACT-CGA-TT-5’ mRNA 5’-AUG-CUA-CUA-GCU-UAC-CUA-UUC-GAU-UCU-ACC-UGA-GCU-AA-3’ Protein N-met-leu-leu-ala-tyr-leu-phe-asp-ser-thr-C Such a mutation leads to a mutant protein with a completely different C-terminal amino acid sequence as compared to the wild-type protein. In the example above, the mutation also leads to the "creation" of a termination codon which causes the mutant protein to be shorter than the wild type protein. This is expected to have a major effect on protein structure and function unless the mutation occurs close to the C-terminus. (b) Deletion of two nucleotide pairs-same effect as (a). DNA 3’-TAC-GAT-ATC-GAA-TGG-ATA-AGC-TAA-GAT-GGA-CTC-GAT-T-5’ mRNA 5’-AUG-CUA-UAG-CUU-ACC-UAU-UCG-AUU-CUA-CCU-GAG-CUA-A-3’ Protein N-met-leu-C (c) In contrast, deletion of three nucleotide pairs only changes 1 amino acid in the protein, eg. DNA 3’-TAC-GAT-TCG-AAT-GGA-TAA-GCT-AAG-ATG-GAC-TCG-ATT-5’ mRNA 5’-AUG-CUA-AGC-UUA-CCU-AUU-CGA-UUC-UAC-CUG-AGC-UAA-3’ Protein N-met-leu-ser-leu-pro-ile-arg-phe-tyr-leu-ser-C The effect on protein structure and function is hard to predict for reasons discussed in class. The deletion of 1 amino acid may have no effect unless it involves a critical amino acid, eg. in the active site of an enzyme. Note:
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M201PS6Answers2008 - MICB 201 Chapter 6 Answers Problem#1...

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