Question

The following DNA sequence (5' $\to$ 3') specifies part of a protein coding sequence, starting from position 1. Which of the following mutations will give rise to a protein that is shorter than the full-length protein?

1	2	3	4	5	6	7	8	9	10	11	12	13	14	15
A	T	G	C	A	A	C	A	T	A	T	A	G	C	T

• A. Deletion of nucleotide 13
• B. Deletion of nucleotide 8
• C. Insertion of a single nucleotide between 3 and 4
• D. Insertion of a single nucleotide between 10 and 11

Answer 1

The correct option is B Deletion of nucleotide 8

The DNA sequence is read in the (5' → 3') direction. The sequence on the DNA is transferred onto the mRNA by the process of transcription. The mRNA is translated with the help of ribosome and the information is used for the formation of protein. When the mRNA is read by the ribosome, the triplet codons are read and accordingly the amino acids are added. The start codon (AUG) is the codon where the ribosome attaches and the transcription is started. When the nucleotide 8 is deleted, the reading frame reads the codon as the stop codon (UGA) and thus, the protein synthesis will be stopped. This will result in formation of a protein with shorter length.

Thus, the correct answer is option B.