Douglas Steinberg | Jul 18, 2004 | 6 min read
A TALE OF TWO MODELS:Courtesy of Douglas K. Bishop and Denise Zickler, © Elsevier ScienceThe double-strand-break repair model (A) posits that during meiotic prophase I, crossovers (COs) and noncrossovers (NCOs) begin with a double-strand break (DSB) of a DNA helix. Cleavage of a structure known as the Holliday junction (HJ) ultimately generates both COs and NCOs. A newer model (B) proposes that COs still arise from HJs (right) but that NCOs come from a pathway called synthesis-dependent str