Chapter 18, Problem 1CONQ

Is each of the following mutations a transition, transversion, addition, or deletion? The original DNA strand is

5′–GGACTAGATAC–3′

(Note: Only the coding DNA strand is shown.)

A. 5′–GAACTAGATAC–3′

B. 5′–GGACTAGAGAC–3′

C. 5′–GGACTAGTAC–3′

D. 5′–GGAGTAGATAC–3′

Summary Introduction

To review:

The kind of mutations that are present in DNA (deoxyribonucleic acid) sequences, while comparing the given sequence $\text{5'-GGACTAGATAC-3'}$ with the following:

A. $5\text{'}\text{-GAACTAGATAC-3'}$

B. $\text{5'-GGACTAGAGAC-3'}$

C. $\text{5'-GGACTAGTAC-3'}$

D. $\text{5'-GGAGTAGATAC-3'}$

Introduction:

Point mutations are a common type of mutation in which, a lone nucleotide in a DNA sequence undergoes change. There could be addition of a nucleotide, deletion of a nucleotide or conversion of one nucleotide into another (transition and transversion mutations).

Explanation of Solution

Mutation is defined as the occurrence of change in the genetic material of an organism, which generally is of permanent nature. Further, more the different types of mutations, which might have occurred in the mentioned parts have been described below:

A. When the given sequence is compared with the new sequence, $5\text{'}\text{-GAACTAGATAC-3'}$, at the second position, there is a point mutation which converts G (guanine) to A (adenine). This mutation is a transition mutation, since, one purine nucleotide (G) is changing into another purine nucleotide (A).

B. On comparing the given sequence to the new sequence, $\text{5'-GGACTAGAGAC-3'}$, there is a mutation at the ninth position, wherein, T (thymine) is changing into G. This is called a transversion mutation, since, a pyrimidine nucleotide (T) is changing into a purine nucleotide (G).

C. When compared with the new sequence, $\text{5'-GGACTAGTAC-3'}$, the eighth nucleotide in the given sequence is missing from the new sequence indicating that, this is a deletion mutation.

D. On comparing with the new sequence, $\text{5'-GGAGTAGATAC-3'}$, it is clear that at the fourth position in the given sequence, there is a transversion mutation, since, a C (cytosine), which is a pyrimidine nucleotide, is getting converted into a G, which is a purine nucleotide.

Conclusion

Therefore, it can be concluded that mutations in the given sequences when compared to the reference sequence are: transition, transversion, deletion and transversion, respectively.