A Locked-Loop Configuration in Salivary-Gland Chromosome 2R of Drosophila melanogaster

An intercalary locked-loop configuration, produced in salivary-gland chromosome 2R of Drosophila melanogaster, suggests that patterns of somatic pairing and of non-homologous association are established at about the same time in the course of development. Assumedly this is not later than the early second-instar larval stage. A high degree of polyteny is subsequently attained while the chromosome is locked in a tight loop configuration.