Patterns of puffing activity and chromosomal polymorphism in Drosophila subobscura II. Puffing patterns at the prepupa stage

Puffing activity patterns of the five large polytene chromosomes of Drosophila subobscura were studied during the late third-larval instar and through the prepupal period. A total of 166 loci active in some of the eleven stages studied were described. The distribution of these active loci per chromosome is the following: 25 on chromosome A, 33 on chromosome J, 31 on chromosome U, 34 on chromosome E and 43 on chromosome O. Seven principal patterns of puffing activity were defined taking into account the different curves of the puffing histograms. Gene activities per chromosome as well as total were analysed. Three peaks of gene activity at the beginning, middle and ending of prepupation can be observed. U is the most active chromosome and A (the sex chromosome), and J the least active. Chromosomes E and O show a medium activity. A possible biological explanation for these results is discussed.Publication No. 107, Departamento de Genética, Universidad de Valencia (Spain).