Most CNV regions had simple patterns of segments across individuals on chromosomes, as illustrated in Figure 1B.
The pattern of segment fusion that forms chelicerates' heads is unique among arthropods, and what would normally be the first head segment disappears at an early stage of development, so that chelicerates lack the antennae typical of most arthropods.
However, they found that the pattern of segment usage was almost identical between two different individuals.
Duboule had spent decades studying Hox genes, and the way they generated the pattern of segments in an animal: from head to tail, with more genes being switched on in each successive segment.
Geneticists homed in on the mutations in DNA which were producing these bizarre, mutant flies – and they discovered genes which controlled the pattern of segments in the normal fly embryo.
Arthropods also have two body elements that are not part of this serially repeated pattern of segments, an acron at the front, ahead of the mouth, and a telson at the rear, behind the anus.
Each point of B corresponds to a 3-torus, except for infinitely many "bad" points which form a grid-like pattern of segments on the Calabi Yau and correspond to singular tori.
If a common origin with trunk segments is true, one can expect that at least a part of the genes and signaling pathways that are used for the early embryonic and larval patterning of segments and pygidium will be similar.
Interactions between morphogen gradients produced by some of these proteins determine anterior-posterior and dorsal-ventral patterning of segments (Sanicola et al., 1995; Shirras and Couso, 1996; Struhl et al., 1997; Kopp et al., 1999; Ninov et al., 2010).
Analysis of expression patterns of key segment polarity genes engrailed (en) and wingless (wg) revealed substantial differences between WT and mutant embryos.
