Base analogs may cause mutations because
A. they insert themselves between adjacent bases on the DNA strand and cause an extra base to be inserted during replication.
B. they may exist in alternate chemical states that pair with different DNA bases than the normal state during replication.
C. they remove amino groups from bases, causing them to pair with the wrong base during replication.
D. they modify the chemical structure and properties of the normal base.
E. Both A and C

Base analogs are structurally similar chemical mutagens of one of the Nitrogenours Bases (adenine guanine cytosine or thymine). The analogs compete for the place of normal nitrogenous base during replication and induce a base substitution mutation in 1st round of replication.

E: 5-bromouracil incorporated in to the place of thymine and base pair with guanine, while thymine base pair with adenine according wobble base pairing rule. In the subsequent round of replication guanine will base pair with cytosine leading to base substitution mutation and 5-bromouracil might be excised leading to frame shift mutation.

2- aminopurine an analog of adenine can base pair with thymine or cytosine. (according wobble base pairing rule adenine does not base pair with cytosine).