THE BASE COMPOSITION OF NUCLEIC ACIDS IN CHROMOSOMES, PUFFS, NUCLEOLI, AND CYTOPLASM OF CHIRONOMUS SALIVARY GLAND CELLS

Abstract

The base composition of RNA from individually isolated giant chromosomes, puffed chromosome segments, nucleoli, and samples of cytoplasm from Chironomus salivary gland cells was determined by microelectrophoresis. Data on the adenine :guanine quotient of the chromosomal DNA were also obtained. The results show that: 1) Chromosomal, nucleolar, and cytoplasmic RNA's differ significantly from each other in base composition. 2) Nucleolar and cytoplasmic RNA's, in spite of the difference, show great similarities with regard to the base composition and are both rich in adenine and uracil.3) The RNA extracted from chromosome I differs significantly from the RNA's extracted from different segments of chromosome IV, and the latter differ significantly from each other. 4) The values for the RNA-DNA quotients of chromosome segments parallel the development of synthetically active genes, so-called Balbiani rings. 5) The chromosomal RNA does not show a base symmetry in any of the investigated eases, nor is the content of guanine + cytosine the same as that for DNA. The first of these two facts excludes the possibility that the chromosomal RNA is a complete copy of both strands of the chromosomal DNA. In spite of the difference in guanine -I-cytosine content between the two nucleic acids the RNA may still partly or completely be a single strand copy depending upon how representative the DNA values are for the synthetically active DNA.

STUDIES ON PUFFING IN THE SALIVARY GLAND CHROMOSOMES OF <i>DROSOPHILA ANANASSAE</i>

“…Investigations of puffing patterns in several species of Diptera have shown them to be specific with respect to developmental stages as well as to tissues (Beermann 1952;Breuer and Pavan 1955;Becker 1959). Beermann's original hypothesis, that a puff is the visible expression of genetic materials located at that site, has been confirmed by other studies (Edstrom and Beermann 1962;Pelling 1964;Stevens and Swift 1966).…”

THE DNA BASE COMPOSITION OF INDIVIDUAL CHROMOSOMES AND CHROMOSOME SEGMENTS FROM CHIRONOMUS TENTANS

“…For dissection of chromosome segments this fixation was found to be unsuitable, not permitting an accurate delineation of segments. Therefore part of the material was on May 12, 2018 jcb.rupress.org Downloaded from fixed with formaldehyde as described by Edström and Beermann (5) . After fixation, the glands were rinsed in three successive baths of distilled water, each for 10 min.…”

The development and application of a silver-aldehyde reaction for the study of chromosome ultrastructure

“…The adenine/uracil ratio of the RNA fraction of the Balbiani rings of Chironomus has been shown to differ from that of the RNA of both the nucleolus and the cytoplasm (EdStrom and Beermann, 1962). In fact, each of the three Balbiani rings of the fourth salivary gland chromosome contain distinctly different fractions of RNA as determined by RNA base-ratio analysis.…”

“…somes (Beermann, 1957, Swift, 1961. Evidence from a number of investigations suggests that the Balbiani ring represents a single active genetic locus on the chromosome (Beermann, 1957, Edstrom and Beermann, 1962.…”