Question

A point mutation comprising substitution of purine with pyrimidine is called as

• A. Transition
• B. Transversion
• C. Deletion
• D. Translocation

Answer 1

The correct option is B Transversion

The transition is the substitution of one type of base by other of its own type. Hence, purine is replaced with purine (adenine to guanine and vice versa) and pyrimidine is replaced with a pyrimidine (cytosine to thymine/uracil and vice versa) only; option A is incorrect. Substitution of purine base for a pyrimidine base or substitution of pyrimidine base for a purine base is called as transversion. Hence, adenine is replaced with thymine/ uracil and guanine with cytosine which makes option B correct. Rearrangement of the chromosomal segment between two non-homologous chromosomes is called as translocation; option C is incorrect. Removal of one or more nucleotide bases to the DNA segment is known as deletion. It can remove one to many nucleotide bases from the DNA resulting in shortening of the encoded proteins which are mostly non-functional which makes option C wrong. The correct option is B.