Figure 6.

Possible mechanisms of extension from two to three 34 bp tandem repeats (TRs) in the promoter region of the cyp51A gene during the mitotic cell cycle. (A) Replication slippage: when strand slippage occurs during DNA replication in the S-phase of the mitotic cell cycle, a DNA strand with the repeat may loop out resulting in addition of the repeat number [15]. (B) Unequal sister chromatid recombination: during the S/G2 phase, unequal crossing over may occur between the repeats of the sister chromatids resulting in an extra copy of the repeat on one chromatid.