Puffing pattern of 0-hour prepupae of Drosophila melanogaster.

Puffs were scored from prepupae of a homogeneous stage concerning both chronological and developmental age. In the Finnish strain of D. melanogaster, Porvoo wild, altogether 121 loci were observed to be puffing in the giant salivary chromosomes at the beginning of the prepupal stage. 86 of the puffs revealed a regular constancy in their activity. The results are in agreement with earlier analyses except for five puffs 23C (in 2L), 42C, 46D, 47F (in 2R) and 61F (in 3L) not reported in previous puff data. Special attention is paid to the degree of interindividual variation of puff size. The range of variability in size of different puffs is not uniform. Eight loci show especially wide variation while there are approximately twenty loci which, instead, show remarkable constancy between prepupae.