Figure 7.

Palindrome-mediated DNA amplification occurs via template switching in rad27Δ strains. In this example, found at chrVII: 657,551, DNA amplification is the dominant outcome. (A) Two different subculture 25 strains are shown: the top line is the mutated sequence and includes an insertion mediated by a palindrome, and the bottom line is the original sequence. Arrows indicate palindromes, brackets indicate duplication, and numbers indicate important points in the mechanism. (B) DNA synthesis starts on a template similar to the bottom line in A and continues until the fork is stalled (point 1). (C) At point 2, the DNA folds back (template switch #1) (D) and synthesizes until it arrives at point 3. (E) The nascent strand aligns back to the top strand (template switch #2) at point 4 (F) and continues synthesis in the original direction. The top strand resembles the bottom and original sequence in A, and the bottom strand resembles the top and mutated sequence in A. The next round of replication results in two daughter cells with the rearrangements depicted in A. The red strand is the nascent strand and the blue strand is the original template strand.