Answer: The correct answer is Substitution point mutation.
Mutation is the permanent change in the genetic material of the organism. Point mutation means there is change in one nucleotide sequence and substitution mutation means replacement of one or more bases by the same number.
As per the question, mutation has occurred in the DNA coding for the fourth codon ( which is ccu in the mRNA sequence).
The fourth codon is changed from ccu to acu. This indicates that there is change in one nucleotide that is from c ( cytosine) to a ( adenine) and also it is a substitution mutation as cytosine is replaced by adenine.
