Question

A small section of a gene for a protein has the following nucleotide sequence:

CCT AAG GAT TCA CTT

Which of the following mutations would cause a missense mutation in the sequence shown above?

Select one:

a. Replacement of second thymine base with adenine base

b. Replacement of second guanine base with adenine base

c. Replacement of first thymine base with cytosine base

d. Replacement of first guanine base with cytosine base

I thought a?

A small section of bacterial DNA template (anti-sense) strand has the following nucleotide sequence:

AAG TAT TAT GCA

A mutation in the above sequence involved the insertion of a single base, leading to a shift in the reading frame of the gene, resulting in altered amino acids downstream from the insertion.

Which of the following gene sequences exemplifies the mutation described above?

Select one:

a. AAG TAT UTA TGC A

b. AGT ATT ATG CA

c. AAG TAT TAC GCA

d. AAG CTA TTA TGC A

A small section of Saccharomyces cerevisiae gene has the amino acid sequence valine, histidine, cysteine, and lysine.

A mutation in the above section of the amino acid sequence resulted in the substitution of amino acid lysine with amino acid asparagine.

The mutation in the antisense strand DNA of Saccharomyces cerevisiae gene described above involves

Select one:

a. the substitution of second thymine base from TTC

b. the substitution of second adenine base from AAG

c. the substitution of guanine base from AAG

d. the substitution of cytosine base from TTC

Answer 1

Answer 1: missense mutation  is a point mutation in which change in a single nucleotide results in a codon that codes for a different amino acid.

In option ( a). Replacement of second thymine base with adenine base---GAT to GAA (Aspartate to glutamate)

In option (b)Replacement of second guanine base with adenine base- GAT to AAT (Aspartate to asparagine)

In option (c) Replacement of first thymine base with cytosine base-CCT to CCC (proline to proline ).

In option (d) Replacement of first guanine base with cytosine base -AAG to AAC( lysine to asparagine).

So except option (c) all other options (a) (b) &(d) are example of missense mutation while option (c) is example of same sense mutation.

Answer 2: Insertion of nucleotide in base sequence results in frame shift mutation.

Correct option is (a). In option (c) substitution of nucleotide T to C occurs not insertion of nucleotide. All other options are not correct .

Answer 3: correct option is (c)the substitution of guanine base to cytocin base from AAG to AAC.All other options are not correct according to given explanation.