Question

4. It is common for scientists to work backwards to find a Rene of interest. They stan determining the sequence of amino acids in a protein that interests them. From the amino acid sequence, they can determine possible mRNA codons and then determine the possible DNA sequence for the gene of interest. They can then construct the gene and express it in a plant or microbe so that they can produce larger quantities of the protein. Indicate one possible mRNA codon and the DNA base triplet for each amino acid. 

 5. Consider the following hypothetical gene. Transcribe the DNA to form mRNA codons, and then give the sequence of amino acids that forms the polypeptide during translation 

T-A-C-T-T-A-C-C-G-T-C-A-A-T-C 

mRNA codons _______ 

Amino acid sequence _______ 

6. For the following mutations in the gene above, show the effect of the mutation by indicating the mRNA codons and the amino acid sequence. 

a. base substitution T-A-C-T-T-A-C-C-G-T-C-G-A-T-C 

mRNA codons _______ 

Amino acid sequence _______ 

b. base insertion T-A-C-T-T-A-T-C-C-G-T-C-A-A-T-C 

mRNA codons _______ 

Amino acid sequence _______ 

Answer 1

4.

Note, the DNA triplets are from the non-coding strand or the template strand

Amino Acid	mRNA codon	DNA base triplet
Lysine	AAA	TTT
Serine	UCU	AGA
Arginine	CGU	GCA
Valine	GUU	CAA

Note: for the next set of questions, it is assumed that the DNA given is from the non-coding strand or the template strand.

5.

DNA : TAC-TTA-CCG-TCA-ATC

mRNA : AUG-AAU-GGC-AGU-UAG

Protein : Methionine (M) - Asparagine (N) - Glycine (G) - Serine (S) - STOP (.)

6.

• DNA : TAC-TTA-CCG-TCG-ATC
  mRNA : AUG-AAU-GGC-AGC-UAG
  Protein : Methionine (M) - Asparagine (N) - Glycine (G) - Serine (S) - STOP (.)

• DNA : TAC-TTA-TCC-GTC-AAT-C
  mRNA : AUG-AAU-AGG-CAG-UUA-G
  Protein : Methionine (M) - Asparagine (N) - Arginine (R) - Glutamine (Q) - Leucine (L)
  
  Here, we see a frameshift mutation due to the insertion of a base in the middle of the DNA sequence.