WHOLE MOUNT ELECTRON MICROSCOPY OF POLYTENE CHROMOSOMES FROM DROSOPHILA MELANOGASTER

1976 ◽  
Vol 18 (1) ◽  
pp. 67-77 ◽  
Author(s):  
Gary D. Burkholder
Keyword(s):  
Electron Microscopy ◽  
Drosophila Melanogaster ◽  
Polytene Chromosomes ◽  
Ultrastructural Level ◽  
Structural Features ◽  
Gene Localization ◽  
Simple Method ◽  
Longitudinal Orientation ◽  
Whole Mount ◽  
Chromosome Bands

A simple method of whole mount electron microscopy has been developed to study the fine structural organization of Drosophila melanogaster polytene chromosomes. This method preserves the structural features of these chromosomes and may be of use for rapid gene localization at the ultrastructural level. Chromosome bands were electron dense regions composed of closely packed groups of chromomeres; thin bands consisted of a single row of transverse chromomeres, while thicker bands were composed of two to several rows of chromomeres. Interband regions contained relatively straight chromatin fibres which traversed the interband zone either singly or in bundles of several fibres. The interband chromatin fibres were generally 130 Å in diameter or thicker, and appeared to be composed of two or more thinner (80-90Å) fibres. Presumptive puff regions were characterized by extended chromatin fibres having a longitudinal orientation, however some transverse rows of chromomeres were also seen in these regions, suggesting that not all of the chromomeres in a band may be involved in puff formation. The chromatin fibres in the puffs were frequently thinner than those found in the interband regions. In stretched chromosomes, the chromatin fibres were drawn out into a mass of parallel fibres without any distinction between band and interband regions, supporting the hypothesis that individual chromatids are continuous through both band and interband regions and probably extend throughout the whole chromosome. No core fibres were observed in any of the polytene chromosomes studied.

scholarly journals Identifiable regions of Drosophila melanogaster polytene chromosomes visualized by whole mount electron microscopy

Hereditas ◽  
2009 ◽  
Vol 89 (2) ◽  
pp. 257-261 ◽  
Author(s):  
Markku Alanen ◽  
Veikko Sorsa
Keyword(s):  
Electron Microscopy ◽  
Drosophila Melanogaster ◽  
Polytene Chromosomes ◽  
Whole Mount

Structure of Drosophila polytene chromosomes. Evidence for a toroidal organization of the bands

1982 ◽  
Vol 57 (1) ◽  
pp. 73-113
Author(s):  
L.I. Mortin ◽  
J.W. Sedat
Keyword(s):  
Electron Microscopy ◽  
Fluorescent Microscopy ◽  
Polytene Chromosomes ◽  
Three Dimensional ◽  
Structural Features ◽  
Serial Sections ◽  
High Voltage Electron Microscopy ◽  
Voltage Electron ◽  
Chromosome Bands ◽  
Whole Mounts

Avoiding acid fixation or squashing, the structure of Drosophila salivary gland polytene chromosomes has been examined in detail in nuclei, with special emphasis on the organization of the DNA in the chromosome bands. Cut serial sections, optical serial sections, scanning electron microscopy (SEM) on whole mounts, high-voltage electron microscopy (HVEM) on whole mounts, and pancreatic DNase I digestion monitored by fluorescent microscopy have been used to complement one another in this analysis. With all five of these techniques, stereo pairs were used to aid in the three-dimensional reconstruction of chromosomal structures. Evidence is presented that most, if not all, of the polytene chromosome bands are torus-shaped. The DNA of these bands is largely confined to the rim, with the interior essentially DNA-free. The chromatin in each polytene band is also seen to have an extremely regular and highly ordered substructure. This substructural organization is largely radially symmetric in the bands and generally parallel to the chromosome axis. In addition, each band appears to be a distinct architectural entity with regard to its exact structural features and dimensions. A model is presented that follows these organizational boundary conditions.

WHOLE MOUNT ELECTRON MICROSCOPY OF THE NUCLEOLUS IN SALIVARY GLAND CELLS OF DROSOPHILA MELANOGASTER

1977 ◽  
Vol 19 (1) ◽  
pp. 21-29 ◽  
Author(s):  
Gary D. Burkholder
Keyword(s):  
Electron Microscopy ◽  
Drosophila Melanogaster ◽  
Salivary Gland ◽  
Peripheral Region ◽  
Core Region ◽  
28S Rrna ◽  
The Core ◽  
Gland Cells ◽  
Salivary Gland Cells ◽  
Whole Mount

The nucleolus of Drosophila melanogaster salivary gland cells, examined by whole mount electron microscopy, consists of a fibrillar core region and a peripheral region containing both fibres and granules. These regions appear to correspond to the fibrillar and granular components, respectively, seen in thin sections. Most of the nucleoli were attached to the chromocenter region of the polytene chromosomes, containing the nucleolar organizer. Bundles of relatively straight chromatin fibres, 13 nm in diameter, extended from the chromocenter into the core region of the nucleolus, however it was not possible to trace the path of these chromatin fibres through the nucleolus since they were obscured within the mass of nucleolar fibres. The nucleolar fibres in both the core and peripheral regions were irregular and knobby, with a diameter of about 15 nm. In the core region, the fibres appeared to be of considerable length and were characteristically clustered together to form small interconnected masses. The fibres in the peripheral region were relatively short and some appeared to blend with amorphous, poorly-defined pools of material. Electron dense granules 15-20 nm in diameter were also associated with this amorphous substance. It is hypothesized that the formation and subsequent packaging of the 28s rRNA may be represented by a morphological transition of the peripheral fibres, via an amorphous pool-like intermediate stage, into the nucleolar granules. The results of this study indicate that whole mount electron microscopy may be a useful alternative to thin sectioning in high resolution studies of the nucleolus.

scholarly journals Whole mount electron microscopy of alkali-urea treated polytene chromosomes spread by centrifugation

Hereditas ◽  
2009 ◽  
Vol 82 (1) ◽  
pp. 131-135 ◽  
Author(s):  
Veikko Sorsa ◽  
Virpi Virrankoski-Castrodeza
Keyword(s):  
Electron Microscopy ◽  
Polytene Chromosomes ◽  
Whole Mount

Structural features of 3C6/C7 interband chromatin organization in Drosophila melanogaster polytene chromosomes

2013 ◽  
Vol 7 (4) ◽  
pp. 347-351 ◽  
Author(s):  
O. V. Andreenkov ◽  
E. I. Volkova ◽  
V. F. Semeshin ◽  
I. F. Zhimulev ◽  
S. A. Demakov
Keyword(s):  
Drosophila Melanogaster ◽  
Polytene Chromosomes ◽  
Structural Features ◽  
Chromatin Organization

scholarly journals Motor domain phosphorylation and regulation of the Drosophila kinesin 13, KLP10A

2009 ◽  
Vol 186 (4) ◽  
pp. 481-490 ◽  
Author(s):  
Vito Mennella ◽  
Dong-Yan Tan ◽  
Daniel W. Buster ◽  
Ana B. Asenjo ◽  
Uttama Rath ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Cell Cycle ◽  
Molecular Dynamics ◽  
Drosophila Melanogaster ◽  
Structural Features ◽  
Motor Domain ◽  
Α Helix ◽  
Dynamics Simulations

Microtubule (MT)-destabilizing kinesin 13s perform fundamental roles throughout the cell cycle. In this study, we show that the Drosophila melanogaster kinesin 13, KLP10A, is phosphorylated in vivo at a conserved serine (S573) positioned within the α-helix 5 of the motor domain. In vitro, a phosphomimic KLP10A S573E mutant displays a reduced capacity to depolymerize MTs but normal affinity for the MT lattice. In cells, replacement of endogenous KLP10A with KLP10A S573E dampens MT plus end dynamics throughout the cell cycle, whereas a nonphosphorylatable S573A mutant apparently enhances activity during mitosis. Electron microscopy suggests that KLP10A S573 phosphorylation alters its association with the MT lattice, whereas molecular dynamics simulations reveal how KLP10A phosphorylation can alter the kinesin–MT interface without changing important structural features within the motor’s core. Finally, we identify casein kinase 1α as a possible candidate for KLP10A phosphorylation. We propose a model in which phosphorylation of the KLP10A motor domain provides a regulatory switch controlling the time and place of MT depolymerization.

scholarly journals Toroidal bands in polytene chromosomes of Drosophila

1983 ◽  
Vol 64 (1) ◽  
pp. 255-264
Author(s):  
V. Sorsa
Keyword(s):  
Electron Microscopy ◽  
Drosophila Melanogaster ◽  
Salivary Gland ◽  
Thin Section ◽  
Polytene Chromosomes ◽  
Thin Sections ◽  
Sister Chromatids ◽  
Thin Section Electron Microscopy ◽  
Section Electron ◽  
Section Electron Microscopy

Results obtained from the thin-section electron microscopy of salivary gland chromosomes of Drosophila melanogaster mainly support the concept of cable-like organization of polytene chromosomes, with disk-like bands composed of parallel bundles of homologous chromomeres. Outward orientation of loop fibres may generally cause a toroidal bending in the chromomere bundles. Both longitudinal and transverse sections of polytene chromosomes indicate that the bands may contain toroidal subunits. Torus-shaped bands were only found in thin sections of the most distal and most proximal regions, as well as in certain heavy bands at the late-replicating regions of polytenized interphase chromosomes. This suggests that an incomplete duplication of chromomeres may be a reason for torus formation, by preventing the separation of sister chromatids at the earliest phases of the polytenization process. The appearance of more numerous, but smaller, subunits in thin-sectioned faint bands is interpreted as a consequence of more complete segregation of sister chromatids in those bands during polytenization.

The polytenic endosperm haustorium of Rhinanthus minor (Scrophulariaceae): functional ultrastructure

1992 ◽  
Vol 70 (10) ◽  
pp. 1997-2004 ◽  
Author(s):  
Walter Nagl
Keyword(s):  
Polytene Chromosomes ◽  
Ultrastructural Level ◽  
Structural Features ◽  
Synthetic Activity ◽  
Apical Region ◽  
Nuclear Surface ◽  
Chalazal Haustorium ◽  
Endosperm Haustorium ◽  
Micropylar Endosperm ◽  
Giant Nuclei

The seed of Rhinanthus undergoes an uncommon differentiation in developing both a chalazal and a micropylar endosperm haustorium. The chalazal haustorium is described at the ultrastructural level. It shows two giant nuclei with polytene chromosomes and numerous complex nucleoli. The nuclear surface is highly interdigitated with the cytoplasm and displays many pores. The cell wall of the apical region of the haustorium displays a prominent wall labyrinth. A large number of mitochondria are located in this region, while leucoplasts are mainly found in vicinity of the nuclei. The structural features of the haustorium are discussed in relation to its expected functions, i.e., synthetic activity and transfer of nutritive material from surrounding tissues to the endosperm proper. Key words: endosperm, haustorium, polyteny, Rhinanthus, transfer cell.

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