To understand what causes a frameshift mutation, we need to first understand what a frameshift mutation is.
A frameshift mutation is a type of genetic mutation wherein a number of nucleotides that is not a multiple of three are inserted or deleted from a DNA sequence. Because the genetic code is read in groups of three nucleotides, called codons, any addition or deletion that does not occur in multiples of three will disrupt the reading frame. This results in a completely different translation from the original.
In the given options, the potential causes for frameshift mutations are:
5-Bromouracil: It is a base analog that typically causes point mutations by substituting for thymine and pairing with guanine.
Acridine: Acridine and its derivatives (such as acridine orange) are known as intercalating agents. They insert themselves between DNA base pairs, causing additions or deletions of nucleotide pairs, resulting in frameshift mutations.
Glutathione: It is an antioxidant that protects cells from oxidative damage; it does not cause frameshift mutations.
Hypoxanthine: A product of adenine deamination, it can cause base substitution mutations but not frameshift mutations.
From the options, Acridine is the correct answer as it causes frameshift mutations by intercalating into DNA and disrupting the base-pairing, leading to insertions or deletions.