DEVELOPMENT, STRUCTURE AND COMPOSITION OF LAMPBRUSH CHROMOSOMES IN DOMESTIC FOWL

Abstract

Stained sections of developing ovaries and hand-isolated oocyte nuclei and lampbrush chromosomes of domestic fowl were studied. The observations suggest a synchronous transformation from the diplotene chromosomes to the lampbrush stage of chromosomal development and an asynchronous breakdown of recognizable chromosomes in larger oocytes.Before the appearance of lampbrush chromosomes a series of nucleo-cytoplasmic changes were observed in the developing oocytes. Formation and dispersal of the Balbiani-body complex in the cytoplasm appears to be associated with the movement of chromosomes and the initiation of lampbrush formation.The lampbrush chromosomes are developed early in life, in about 18-day chicks, and continue to be observed in active oocytes (above 150 μ diam) of mature birds. The lateral loops of lampbrush chromosomes appear to contain nucleoprotein chromatic granules in linear array. Using enzyme treatment it is conceived that the protein composition of the lampbrush chromosome is relatively higher than is observed in other species and that nucleoprotein synthesis can take place in several segments of a single loop of the avian lampbrush chromosome.