Question: A point mutation which involves change \[A \to G,C \to T,C \to G\] and \[T \to A\] in DNA are A) T...

Question

A point mutation which involves change $A \to G,C \to T,C \to G$ and $T \to A$ in DNA are
A) Transition, Transition, Transversion, Transversion
B) Transition, Transversion, Transition, Transversion
C) Transversion, Transition, Transversion, Transition
D) None of the above

Answer 1

Solution

The DNA is made up of two different types of nitrogenous bases that are purines and pyrimidines. The purines are of two types which are Adenine (A) and Guanine (G). The pyrimidines are also of two types which are Cytosine (C) and Thymine (T) (in DNA) or Uracil (U) (in RNA).

Complete answer: The exchange of nitrogenous bases with one another is known as substitution. It is of two types; transition and transversion. The transition is that type of substitution in which the base of a similar type is exchanged with another. It means that the purine is exchanged with another purine and the pyrimidine is exchanged with another pyrimidine. The transversion is that type of substitution, in which the bases of dissimilar types are exchanged with one another. It means that a purine is exchanged with pyrimidine and vice versa.
a) $A \to G$ :
Adenine and Guanine are both purine bases. The exchange of similar bases is a transition substitution.
b) $C \to T$ :
Cytosine and Thymine are both pyrimidine bases. The exchange of similar bases is a transition substitution.
c) $C \to G$ :
Cytosine is a pyrimidine base and Guanine is a purine base. The exchange of dissimilar bases is transversion substitution.
d) $T \to A$ :
Thymine is a pyrimidine base and Adenine is a purine base. The exchange of dissimilar bases is a transversion substitution.
Thus, based on the above information, we can conclude that a point mutation that involves change $A \to G, C \to T, C \to G$ and $T \to A$ in DNA are transition, transition, transversion, and transversion respectively.
Hence, the correct answer is option A.

Note: The DNA is made up of a basic unit known as the nucleotide. The nucleotide has three components that are the nitrogenous base, pentose sugar (deoxyribose) and a phosphate group. Nitrogenous bases are further divided into purines and pyrimidines.