Question

4. A polypeptide has the following amino acid sequence: Met-Ser-Pro-Arg-Leu-Glu-Gly In the mutant below, indicate the type of mutation that occurred in the DNA and the phenotypic effect of the mutation Met-Ser-Pro-Asp-Trp-Arg-Asp-Lys a. Single base substitution/nonsense mutation b. Insertion/missense mutation c. Deletion/ frameshift mutation d. Deletion/missense mutation e. Single base substitution/frameshift mutation A non template strand on bacterial DNA has the following base sequence. What amino acid sequence will be encoded by this sequence? 5. 5-ATG ATA CTA AGG CCC-3 a. Tyr Tyr Asp Ser Gly b. c. d. e. Met Ile Leu Arg Pro Met Leu Ile Asp Pro Tyr Val His Stop Met Ile Ile Arg Pro The following mRNA sequence is encoded by a gene Q. 5'-ACUGUAAUGGAGUCAGAUGAUGCAUUAAGGAGAAAUUGAAAUAAA-3' What would be the consequence of adding an extra G (guanine) base to the gene Q sequence immediately after the start codon? a. There was no consequence. b. A frameshift occurred which altered the identity of the amino acids following the initiator 6. methionine, but not the length of protein Q. c. A frameshift occurred which altered the identity of the amino acids following the initiator methionine in protein Q AND shortened it to only eight amino acids. d. Splicing was altered. e. A longer protein.

Answer 1

Answer:

4. c. Deletion/ frameshift mutation

5. a. Tyr Tyr Asp Ser Gly

6. A frameshift occurred which altered the identity of the amino acids following the initiator 6. methionine, but not the length of protein Q.

Explanation:

4)

A single base pair at the first position of the Arg codon i.e. CGA has been deleted. Due to the deletion, the reading frame has shifted one nucleotide backwards, altering the amino acid sequence of the protein.

5)

The genomic DNA sequence is 5'-ATG ATA CTA AGG CCC-3'. Therefore, the complementary mRNA will be 5'-UAC UAU GAU UCC GGG-3'. According to the genetic code, this mRNA sequence encodes the following amino acid sequence: Tyr Tyr Asp Ser Gly

6)

The wild type DNA sequence is:

5'-ACUGUAAUGGAGUCAGAUGAUGCAUUAAGGAGAAAUUGAAAUAAA-3'

The mutant i.e. mRNA with the added G will be

5' ACUGUAAUGGGAGUCAGAUGAUGCAUUAAGGAGAAAUUGAAAUAAA-3'  

This is a single base pair insertion and frameshift mutation that shifts the reading frame one base pair forwards. The codon that was originally GAG coding for glutamic acid (Glu) gets converted to GGA that codes for glycine. Therefore, the amino acid sequence has been altered but the polypeptide chain will still have 13 amino acids.