The chromosomes of two Drosophila races: D. nasuta nasuta and D. nasuta albomicana

Interracial hybridization between Drosophila nasuta nasuta (2n=8) and D. n. albomicana (2n=6) has resulted in the evolution of two new karyotypic strains, called Cytoraces I and II. Males and females of Cytorace I have 2n=7 and 2n=6 respectively. The reconstituted karyotype is totally new in its composition, the chromosomes being drawn from both the parental races. The individuals of Cytorace II have 2n=6. Even though the chromosomes of the parental races are duly represented in the F₁, there is selective retention/elimination of certain chromosomes in the succeeding generations during which repatterning of the karyotype has taken place. Dynamics of each one of the parental chromosomes are presented and its implications re discussed.We dedicate this paper to the memory of the founder of our Department, the late Prof. M.R. Rajasekarasetty on the occasion of the Silver Jubilee of our Department