Question

1) Which of the following mutations could result in a frameshift?

A) a base insertion

B) a base deletion

C) a base substitution

D) either A or B

E) A, B, and C

2) Which of the following point mutations would be most likely to result in a non-functioning protein?

A) a single base substitution in an intron

B) a single base deletion near the end of the coding sequence

C) a single base deletion in the codon following the start codon

D) a single base insertion in the 3'UTR.

E) all of the above would equally result in a non-functioning protein

3) Some mutations are known as nonsense mutations. What would be the result of this particular type of mutation?

A) There would be a different amino acid in the resulting polypeptide.

B) A premature stop codon would result in a shortened polypeptide.

C) There would be no noticeable change in the resulting polypeptide.

D) The reading frame would be altered.

E) A non-functioning, but same size of protein would be produced.

4) Which of the following portion of template DNA would code for the polypeptide sequence phe-leu-ile-val?

A) 5' TTG-CTA-CAG-TAG 3'.

B) 3' AAC-GAC-GUC-AUA 5'.

C) 5' AAA-GAA-TAA-CAA 3'.

D) 5' AAC AAT AAG AAA 3'.

E) 3' AAA-AAT-ATA-ACA 5'.

5) The template strand of a short section of DNA is 5' TTT-CCC-AAA-GGG-TTT-CCC 3'. Which of the following is the amino acid sequence that would result?

A) lys-gly-phe-pro-lys-gly

B) gly-lys-pro-phe-gly-lys

C) phe-pro-lys-gly-phe-pro

D) lys-gly-pro-phe-lys-gly

E) gly-lys-phe-pro-gly-lys

Answer 1

1. D

Frameshift mutation is the type of mutation which changes the reading frame of the peptidyl synthase enzyme due to which whole sequence of amino acid gets changed. Even insertion or deletion of a single or two nucleotide bases leads to frameshift mutation. If three nucleotide bases are inserted or deleted then one complete amino acid is inserted or deleted. It does not leads to change of whole amino acid sequence.

2. C

If mutation occurs near start codon, then whole Amino acid sequence of the protein gets changed due to which the protein will become non functional or abnormal.

If mutation occurs at the end of coding region, then most of the protein is properly synthesized except for the amino acid present at the last.

If any type of mutation occurs in untranslated region or in introns then there is no effect on the protein structure.

3. B

In nonsense mutation in the codon changes in such a way that it leads to the formation of a stop codon. This leads to premature termination of translation resulting in the formation of a truncated peptide.

4. C

​​​​​​Use genetic code table to see which amino acid is coded by which codon.

5. C

from given DNA, mRNA formed will be,

5' UUU CCC AAA GGG UUU CCC 3'

Now use genetic code table to see amino acids.

Note -

Always remember that,

5' to 3' DNA is coding strand and its sequence is similar to mRNA except for T in place of U.

3' to 5' DNA is template strand and is complementary to mRNA. It undergoes transcription to form 5' to 3' mRNA. This mRNA undergoes translation to form amino acids.

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