ABSTRACT
In Drosophila melanogaster, entire compound second chromosomes (2R2L . 2L2R) consist of the entire amount of genetic material normally found on separate homologues, as well as significant amounts of heterochromatin derived from the Y chromosome, joined to a single centromere. Genetic analysis demonstrates that information carried upon the Y chromosome influences the rate of transmission of the compound in the male.
Subject(s)
Chromosomes/physiology , Drosophila melanogaster/genetics , Animals , Female , Genotype , Heterochromatin/physiology , Male , Pedigree , X Chromosome/physiology , Y Chromosome/physiologyABSTRACT
Three new unusual compound chromosomes have been synthesized in Drosophila melanogaster. They consist of two homologous autosomes joined together in the new order: right arm, left arm, centromere, left arm, right arm, for each of the two major autosomes, and one in which chromosomes 2 and 3 have been combined in the order: right arm of 2, left arm of 2, centromere, left arm of 3, right arm of 3. The attachments of the autosomal arms were accomplished by obtaining chromosome breaks at or very close to the ends of the left arms of the autosomes such that no essential chromosome material has been removed; the compounds derived from them are therefore referred to as entire compounds. These large chromosomes are recovered in progeny with frequencies lower than expectation partly because of zygote mortality associated with these chromosomes, and partly because of a failure of spermiogenesis.
Subject(s)
Chromosomes/ultrastructure , Drosophila melanogaster/genetics , Translocation, Genetic , Animals , Genes, Lethal , Karyotyping , Male , Phenotype , SpermatogenesisABSTRACT
Descriptions are presented of four cases of attachment of chromosome material at the ends of normal chromosomes in Drosophila. Since no material appears to be missing from the polytene chromosomes and there are no ill effects to the organism in morphology, viability, or fertility when the chromosome is made homozygous, it is argued that the attachment occurred without the loss of any essential genetic material and that, in all probability, the break at the end of the chromosome occurred within the telomere of the chromosome. These cases may serve as a parallel to cases of apparent terminal breakage and reunion in certain rearrangements in man.
