Chapter 12, Problem 36A

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 36A

Correct answer :

The correct answer is option C. RNA interference

Explanation of Solution

Explanation/justification for the correct answer:

Option C. RNA interference − It is gene regulating mechanism in eukaryotic cells. RNA interference can stop the mRNA from translating its message by binding of single stranded small interfering RNA and protein complex to sequence specific sections of mRNA and cutting it off. It is not a type of mutation.

Hence this is the correct option.

Explanation for incorrect answer:

Option A. base substitution- Substitution is a type of point mutation. This occurs when one base is exchanged for another base. Most substitutions are missense mutations, where the genetic code is altered so that it codes for the wrong amino acid. Other substitutions called nonsense mutation change the codon for an amino acid to a stop codon. These cause translation to stop immediately. Hence this is not the correct option.

Option B. insertions- Insertions are a type of mutation in which 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. Hence this is not the correct option.

Option D. translocation- This is a type of chromosomal mutation in which a part of a chromosome breaks and attaches to a different chromosome. This results in unusual rearrangement of chromosomes. Hence this is not the correct option.