Identifying a major gene on Chromosome 2 that controls the XY pairing in <i>Drosophila ananassae</i> Doleschall, 1858

Drosophila ananassae males have a diploid chromosome number of 2n=8. During the first meiotic division, the X–Y and 4th chromosomes pair to form a stable heterologous chromosome association that ensures normal chromosome segregation. The pairing sites have been extensively studied in D. melanogaster; however, the genetic controlling of the pairing is elusive. This study aimed to identify the gene controlling the X–Y pairing in D. ananassae. In the somatic cell division of the L8 strain of D. ananassae obtained from Sri Lanka, numerical variation in the number of Y and the chromosome 4 was observed among individuals. Five chromosomal types (XX44, XXY44, XXYY44, XXY444, and XXY4) were observed in the females and four (XY44, XO44, XYY44, and XY444) in the males. The chromosomal variation in the L8 strain was attributed to chromosome non-disjunction, resulting from an incomplete pairing of the X and Y chromosomes during male meiosis. The genetic and cytological analyses revealed a major gene controlling to X–Y paring on the right arm of the chromosome 2 in D. ananassae.