Types of Mutations - Practice Questions & MCQ

Point Mutation:

• It occurs as a result of the replacement of one nucleotide by the other in the specific nucleotide sequence of a gene. 
• It is of two types based on base-pair substitution:
  • Transition mutation: When one purine is replaced by another purine or one pyrimidine is replaced by another pyrimidine.
  • Transversion mutation: When one purine is replaced by a pyrimidine and vice versa. 

Frame-Shift Mutation:

• There is another category of the point mutation in which the normal reading frame of the base triplet [codon] is changed. Such mutations are known as frameshift mutations. 
• In these mutations, the normal reading frame of base triplets [codons] is altered due to the addition or deletion of a single base pair of nucleotides in mRNA.

Nonsense Mutation:

• Mutations in which the codon for one amino acid is replaced by a translation termination (stop) codon are referred to as nonsense mutations. 
• In nonsense mutation a stop codon replaces an amino acid codon, resulting in premature termination of the nucleotide chain.

Missense Mutation:

• This type of mutation is a change in one DNA base pair that results in the substitution of one amino acid for another in the protein made by a gene.