Figure 2: Principle of ARMS method and alignment of experimental sequences from W and Z chromosomes. Panel A.- Differential amplification of target sequencefrom Z and W using the ARMS system, distinguishing chromosomes using three NP, MP and P2 primers.NP primer (forward) anchors at the 5´ extreme of thetarget region of both sexes. The MP primer (reverse) have a terminal T that match with the extreme of the W sequence but not with the Z.The P2 primer match withsequence from both sexes. Panel B.- W chromosome products expected in a gel electrophoresis. Panel C.- Alignment of sequences of the region around the MPprimer obtained from both W and Z amplification fragments show that in position 11 could be either a C or a T but it did not disturb the amplification, in contrast tothe key position 20 where the C is specific for Z chromosome and T for W.