Figure 4
A possible evolution path of H20, based on its synteny to M2/R3. The last 50-60-Mb fragment was broken off an ancestral chromosome that evolved to M2/R3. The fragment further split into three pieces with an approximate size of 24, 1.5, and 34 Mb, respectively. Then, the middle 1.5-Mb piece was moved to the tip, inverted, and fused with the 24-Mb piece, forming the p-arm, whereas the 34-Mb piece formed the q-arm. A centromere formed between the two arms where the original middle 1.5 Mb was located.
