Final answer:
Transversion is not a chromosomal mutation; it is a type of point mutation that involves the substitution of a purine for a pyrimidine base, or vice versa, in DNA. The correct option is A.
Step-by-step explanation:
The question 'Which of the following is NOT a chromosomal mutation?' refers to types of genetic changes that occur at the chromosomal level. Chromosomal mutations include deletions, where a segment of a chromosome is lost, duplications.
Which involve the repetition of a chromosome segment, inversions, where a chromosome segment breaks off, reverses, and reattaches, and translocations, which occur when a segment from one chromosome becomes attached to a different chromosome. Among the given options, transversion is NOT a chromosomal mutation, but rather a type of point mutation where one purine base is substituted for a pyrimidine base, or vice versa, in DNA.
Therefore, the correct option is A.