Transition mutation of GATCCT is
Point mutation is of 2 types:-


Transition Purine base is replaced by another purine base or pyrimidine base is replaced by another pyrimidine base.
Transversion Purine base is replaced by pyrimidine base or vice vessa.

In given question,
   GATCCT and GGTCCT  → only option A shows transition mutation
GGTCCT
GTTCCT
GABCCT
GrUGGT