Drosophila has a single copy of the gene encoding a highly conserved histone H2A variant of the H2A.F/Z type.

The Tetrahymena histone H2A variant designated hv1 is localized exclusively in the transcriptionally active macronucleus and is absent from the quiescent micronucleus (1). A cDNA clone of the hv1 gene (2) was used to screen a Drosophila cDNA library. A cross-hybridizing clone was recovered and shown by sequence analysis to code for a protein homologous to hv1 as well as to the chicken H2A variant, H2A.F (3), the sea urchin H2A variant, H2A.F/Z (4) and the mammalian H2A variant H2A.Z (5). Southern analysis of Drosophila genomic DNA indicates that the H2AvD (H2A variant Drosophila) gene is present in one copy. In situ hybridization places the locus at 97CD on chromosome 3, while the S-phase regulated histone genes are on chromosome 2 (6). Thus the Drosophila H2A variant should be accessible to genetic analysis, which will enable its function to be determined.