Chapter 12, Problem 34A

Summary Introduction

Introduction:

A permanent change in the cell’s DNA is called mutation. This change occurs in the nucleotide sequence in DNA. It can be caused by errors in replication, transcription, cell division or by some external agents.

Mutations can occur in single base pair or a large section of DNA may be deleted. Point mutation in one base pair may cause genetic disorder. There are many types of mutations; point mutation, insertions, and deletions.

Answer to Problem 34A

Correct answer :

The correct answer is option D. 5’ GGGCCCAAAAAA 3’

Explanation of Solution

Explanation/justification for the correct answer:

Option D. 5’ GGGCCCAAAAAA 3’- Insertions occurs when a nucleotide is added to the DNA sequence. This type of mutation changes the multiples of three codons from the point of insertion. Hence they are called frame-shift mutation because they change the “frame” of the amino acid. In the given example three adenine nucleotides are added at the end of the given sequence,

5’GGGCCCAAA 3’. Hence this is the correct option.

Explanation for incorrect answer:

Option A. 5’GGGGCCAAA 3’- Here one guanine is added and one cytosine is removed. So there is a substitution and not insertion. Hence this is not the correct option.

Option B. 5’GGGCCAAA 3’- Here one cytosine is removed. So there is a deletion and not insertion. Hence this is not the correct option.

Option C. 5’GGGAAACCC 3’- Here the sequence is changed and there is no insertion. Hence this is not the correct option.