Figure 5

sYG1 is the result of a recent autosome-to-Y duplication. (A) Phylogenetic analysis of bobby sox (bbx) genes from different species. Alignments were produced by Clustalw. Phylogenetic inference was performed using MrBayes v3.1.2. The number near each node is the credibility score provided by MrBayes. Note that Ag_bbx_1 and Ag_bbx_2 are the two An. gambiae autosomal genes AGAP003986 and AGAP003987, respectively. (B) Synteny of the genes located around bobby sox is largely maintained in An. gambiae, An. stephensi, and Aedes aegypti. Genes indicated by the same color are orthologs. The An. gambiae gene names are preceded by AGAP00, the VectorBase gene designations. An. gambiae gene AGAP003897 is in an intron of AGAP003896. A. aegypti orthologs were assigned by VectorBase. An. stephensi orthologs were assigned by our own genome annotation. (C) FISH with a probe designed according to sYG1 hybridized to the An. stephensi Y chromosome. Mitotic chromosome slide preparations were prepared from imaginal discs of 4th instar larvae. Mitotic chromosome FISH was used because the An. stephensi Y chromosome does not polytenize in salivary glands and the ovarian polytene chromosomes do not contain a Y chromosome. (D) The autosomal copy of bobby sox in An. stephensi, AsA-bbx, was mapped to chromosome 2R with FISH on polytene chromosomes. Polytene chromosome slide preparations were obtained using ovaries of half gravid females. From these results we can deduce that AsA-bbx is the ancestral copy of bobby sox in An. stephensi, and that sYG1 is the result of a recent duplication from chromosome 2R to the Y.