Introns can interrupt the reading frame of a gene by inserting a sequence between two consecutive codons (phase 0 introns), between the first and second nucleotide of a codon (phase 1 introns), or between the second and third nucleotide of a codon (phase 2 introns).
Introns can interfere with the flow of genetic information by inserting segments at different locations, such as between codons (phase 0 introns) or within codons themselves (phases 1 and 2 introns).