scholarly journals Large scale synchronous mating and the study of macronuclear development in Euplotes crassus.

1985 ◽  
Vol 101 (1) ◽  
pp. 79-84 ◽  
Author(s):  
M Roth ◽  
M Lin ◽  
D M Prescott
Keyword(s):  
Large Scale ◽  
Average Molecular Weight ◽  
Polytene Chromosomes ◽  
Dna Molecules ◽  
Chromosomal Dna ◽  
Base Pairs ◽  
Macronuclear Development ◽  
Euplotes Crassus ◽  
Large Populations ◽  
Small Size Group

After conjugation in hypotrichous ciliates, a new macronucleus is produced from a copy of the micronucleus. This transformation involves large-scale reorganization of DNA, with conversion of the chromosomal micronuclear genome into short, gene-sized DNA molecules in the macronucleus. To study directly the changes that occur during this process, we have developed techniques for synchronous mating of large populations of the hypotrichous ciliate Euplotes crassus. Electron microscope studies show that the micronuclear chromosomes are polytenized during the first 20 h of macronuclear development. The polytene chromosomes lack the band-interband organization observed in other hypotrichs and in the Diptera. Polytenization is followed by transectioning of the chromosomes. We isolated DNA at various times of macronuclear development and found that the average molecular weight of the DNA decreases at the time of chromosome transectioning. In addition, we have shown that a small size group of macronuclear DNA molecules (450-550 base pairs) is excised from the chromosomal DNA approximately 10 h later in macronuclear development.

Rare internal C4A4 repeats in the micronuclear genome of Oxytricha fallax

1984 ◽  
Vol 4 (12) ◽  
pp. 2661-2667
Author(s):  
D Dawson ◽  
G Herrick
Keyword(s):  
Base Pair ◽  
Full Length ◽  
Dna Molecules ◽  
Base Pairs ◽  
Macronuclear Development ◽  
Structural Relationships

Approximately 20,000 different short, linear, macronuclear DNA molecules are derived from micronuclear sequences of Oxytricha fallax after conjugation. These macronuclear DNAs are terminated at both ends by 20 base pairs of the sequence 5'-dC4A4-3'. Sequences homologous to this repeat (C4A4+) are also abundant in the micronuclear chromosomes, but most reside at their telomeres. Here we show that nontelomeric C4A4 clusters of 20 base pairs or longer exist in only a few hundred copies per micronuclear genome. This demonstrates that nearly none of the 20,000 sequence blocks of micronuclear DNA destined to be macronuclear DNA molecules can be flanked by full-length (20-base pair) C4A4 clusters, and therefore C4A4 repeats must be added to most, if not all, macronuclear telomeres during macronuclear development. Six internal micronuclear C4A4+ loci were cloned, and their structural relationships with macronuclear and micronuclear sequences were examined. The possible origins and functions of these rare, micronuclear internal C4A4 loci are discussed.

scholarly journals DNA rearrangements in Euplotes crassus coincide with discrete periods of DNA replication during the polytene chromosome stage of macronuclear development.

1995 ◽  
Vol 15 (12) ◽  
pp. 6488-6495 ◽  
Author(s):  
J S Frels ◽  
C L Jahn
Keyword(s):  
Dna Replication ◽  
Dna Synthesis ◽  
Polytene Chromosome ◽  
Dna Sequences ◽  
Polytene Chromosomes ◽  
Single Locus ◽  
Dna Rearrangements ◽  
Macronuclear Development ◽  
Euplotes Crassus ◽  
Inhibition Of Dna Synthesis

Macronuclear development in Euplotes crassus begins with polytenization of micronuclear chromosomes and is accompanied by highly precise excision of DNA sequences known as internal eliminated sequences and transposon-like elements (Tecs). Quantitation of radiolabeled-precursor incorporation into DNA indicates that DNA synthesis during formation of polytene chromosomes is not continuous and occurs during two distinct periods. We demonstrate that the timing of Tec excision coincides with these replication periods and that excision can occur during both periods even at a single locus. We also show that Tec and internal eliminated sequence excisions are coincident in the second replication period, thus providing further evidence for similarity in their excision mechanism. Inhibition of DNA synthesis with hydroxyurea diminishes Tec element excision, indicating that replication is an important aspect of the excision process.

scholarly journals Micronuclear genome organization in Euplotes crassus: a transposonlike element is removed during macronuclear development.

1989 ◽  
Vol 9 (9) ◽  
pp. 3793-3807 ◽  
Author(s):  
S E Baird ◽  
G M Fino ◽  
S L Tausta ◽  
L A Klobutcher
Keyword(s):  
Genome Organization ◽  
Frequent Occurrence ◽  
Ciliated Protozoa ◽  
Dna Molecules ◽  
Telomeric Repeats ◽  
Linear Dna ◽  
Macronuclear Development ◽  
Euplotes Crassus ◽  
Close Spacing ◽  
Alternative Processing

After mating, hypotrichous ciliated protozoa transform a set of their micronuclear chromosomes into thousands of short, linear DNA molecules that form the macronuclear genome. To examine micronuclear genome organization in the hypotrich Euplotes crassus, we have analyzed two cloned segments of micronuclear DNA as well as the macronuclear DNA molecules that are derived from them. E. crassus was found to display a number of features characteristic of other hypotrich genomes, including (i) clustering and close spacing of the precursors of macronuclear DNA molecules, (ii) the frequent occurrence of internal eliminated sequences within macronuclear precursors, (iii) overlapping macronuclear precursors, (iv) lack of telomeric repeats at the ends of macronuclear precursors, and (v) alternative processing of the micronuclear chromosome to yield multiple macronuclear DNA molecules. In addition, a moderately repetitive, transposonlike element that interrupts the precursors of two macronuclear DNA molecules has been identified and characterized. This transposonlike element, designated Tec1, is shown to be reproducibly removed from one of the macronuclear precursors during independent episodes of macronuclear development.

scholarly journals Micronuclear genome organization in Euplotes crassus: a transposonlike element is removed during macronuclear development

1989 ◽  
Vol 9 (9) ◽  
pp. 3793-3807
Author(s):  
S E Baird ◽  
G M Fino ◽  
S L Tausta ◽  
L A Klobutcher
Keyword(s):  
Genome Organization ◽  
Frequent Occurrence ◽  
Ciliated Protozoa ◽  
Dna Molecules ◽  
Telomeric Repeats ◽  
Linear Dna ◽  
Macronuclear Development ◽  
Euplotes Crassus ◽  
Close Spacing ◽  
Alternative Processing

After mating, hypotrichous ciliated protozoa transform a set of their micronuclear chromosomes into thousands of short, linear DNA molecules that form the macronuclear genome. To examine micronuclear genome organization in the hypotrich Euplotes crassus, we have analyzed two cloned segments of micronuclear DNA as well as the macronuclear DNA molecules that are derived from them. E. crassus was found to display a number of features characteristic of other hypotrich genomes, including (i) clustering and close spacing of the precursors of macronuclear DNA molecules, (ii) the frequent occurrence of internal eliminated sequences within macronuclear precursors, (iii) overlapping macronuclear precursors, (iv) lack of telomeric repeats at the ends of macronuclear precursors, and (v) alternative processing of the micronuclear chromosome to yield multiple macronuclear DNA molecules. In addition, a moderately repetitive, transposonlike element that interrupts the precursors of two macronuclear DNA molecules has been identified and characterized. This transposonlike element, designated Tec1, is shown to be reproducibly removed from one of the macronuclear precursors during independent episodes of macronuclear development.

scholarly journals Rare internal C4A4 repeats in the micronuclear genome of Oxytricha fallax.

1984 ◽  
Vol 4 (12) ◽  
pp. 2661-2667 ◽  
Author(s):  
D Dawson ◽  
G Herrick
Keyword(s):  
Base Pair ◽  
Full Length ◽  
Dna Molecules ◽  
Base Pairs ◽  
Macronuclear Development ◽  
Structural Relationships

Approximately 20,000 different short, linear, macronuclear DNA molecules are derived from micronuclear sequences of Oxytricha fallax after conjugation. These macronuclear DNAs are terminated at both ends by 20 base pairs of the sequence 5'-dC4A4-3'. Sequences homologous to this repeat (C4A4+) are also abundant in the micronuclear chromosomes, but most reside at their telomeres. Here we show that nontelomeric C4A4 clusters of 20 base pairs or longer exist in only a few hundred copies per micronuclear genome. This demonstrates that nearly none of the 20,000 sequence blocks of micronuclear DNA destined to be macronuclear DNA molecules can be flanked by full-length (20-base pair) C4A4 clusters, and therefore C4A4 repeats must be added to most, if not all, macronuclear telomeres during macronuclear development. Six internal micronuclear C4A4+ loci were cloned, and their structural relationships with macronuclear and micronuclear sequences were examined. The possible origins and functions of these rare, micronuclear internal C4A4 loci are discussed.

The Use of Medical Record Linkage for Population and Genetic Studies

1969 ◽  
Vol 08 (01) ◽  
pp. 07-11 ◽  
Author(s):  
H. B. Newcombe
Keyword(s):  
Record Linkage ◽  
Large Scale ◽  
Medical Record Linkage ◽  
Canadian Province ◽  
Genetic Studies ◽  
Parental Characteristics ◽  
Family Histories ◽  
The Family ◽  
Large Populations ◽  
Machine Readable

Methods are described for deriving personal and family histories of birth, marriage, procreation, ill health and death, for large populations, from existing civil registrations of vital events and the routine records of ill health. Computers have been used to group together and »link« the separately derived records pertaining to successive events in the lives of the same individuals and families, rapidly and on a large scale. Most of the records employed are already available as machine readable punchcards and magnetic tapes, for statistical and administrative purposes, and only minor modifications have been made to the manner in which these are produced.As applied to the population of the Canadian province of British Columbia (currently about 2 million people) these methods have already yielded substantial information on the risks of disease: a) in the population, b) in relation to various parental characteristics, and c) as correlated with previous occurrences in the family histories.

scholarly journals Capture and elongation of single chromosomal DNA molecules using optically driven microchopsticks

2020 ◽  
Vol 14 (4) ◽  
pp. 044114
Author(s):  
Ryo Inukai ◽  
Hidekuni Takao ◽  
Fusao Shimokawa ◽  
Kyohei Terao
Keyword(s):  
Dna Molecules ◽  
Chromosomal Dna

Effects of mutation position on frequency of marker rescue by homologous recombination

1992 ◽  
Vol 12 (8) ◽  
pp. 3609-3613
Author(s):  
L Jiang ◽  
A Connor ◽  
M J Shulman
Keyword(s):  
Homologous Recombination ◽  
Normal Function ◽  
Constant Region ◽  
Dna Fragments ◽  
Wild Type ◽  
End Effect ◽  
Chromosomal Dna ◽  
Base Pairs ◽  
Marker Rescue ◽  
Immunoglobulin Mu

Homologous recombination between transferred and chromosomal DNA can be used for mapping mutations by marker rescue, i.e., by identifying which segment of wild-type DNA can recombine with the mutant chromosomal gene and restore normal function. In order to define how much the fragments should overlap each other for reliable mapping, we have measured how the frequency of marker rescue is affected by the position of the chromosomal mutation relative to the ends of the transferred DNA fragments. For this purpose, we used several DNA fragments to effect marker rescue in two mutant hybridomas which bear mutations 673 bp apart in the exons encoding the second and third constant region domains of the immunoglobulin mu heavy chain. The frequency of marker rescue decreased greatly when the mutation was located near one of the ends of the fragments, the results indicating that fragments should be designed to overlap by at least several hundred base pairs. Possible explanations for this "end effect" are considered.

How damaged is the biologically active subpopulation of transfected DNA?

1984 ◽  
Vol 4 (3) ◽  
pp. 387-398
Author(s):  
C T Wake ◽  
T Gudewicz ◽  
T Porter ◽  
A White ◽  
J H Wilson
Keyword(s):  
Simian Virus 40 ◽  
Simian Virus ◽  
Double Strand Breaks ◽  
Biologically Active ◽  
Exact Nature ◽  
Dna Molecules ◽  
Base Pairs ◽  
Strand Breaks ◽  
Dna Ends ◽  
Prevalent Form

Relatively little is known about the damage suffered by transfected DNA molecules during their journey from outside the cell into the nucleus. To follow selectively the minor subpopulation that completes this journey, we devised a genetic approach using simian virus 40 DNA transfected with DEAE-dextran. We investigated this active subpopulation in three ways: (i) by assaying reciprocal pairs of mutant linear dimers which differed only in the arrangement of two mutant genomes; (ii) by assaying a series of wild-type oligomers which ranged from 1.1 to 2.0 simian virus 40 genomes in length; and (iii) by assaying linear monomers of simian virus 40 which were cleaved within a nonessential region to leave either sticky, blunt, or mismatched ends. We conclude from these studies that transfected DNA molecules in the active subpopulation are moderately damaged by fragmentation and modification of ends. As a whole, the active subpopulation suffers about one break per 5 to 15 kilobases, and about 15 to 20% of the molecules have one or both ends modified. Our analysis of fragmentation is consistent with the random introduction of double-strand breaks, whose cause and exact nature are unknown. Our analysis of end modification indicated that the most prevalent form of damage involved deletion or addition of less than 25 base pairs. In addition we demonstrated directly that the efficiencies of joining sticky, blunt, or mismatched ends are identical, verifying the apparent ability of cells to join nearly any two DNA ends and suggesting that the efficiency of joining approaches 100%. The design of these experiments ensured that the detected damage preceded viral replication and thus should be common to all DNAs transfected with DEAE-dextran and not specific for viral DNA. These measurements of damage within transfected DNA have important consequences for studies of homologous and nonhomologous recombination in somatic cells as is discussed.

Strengthening the Norms of Global Responsibility: Structural Violence in Relation to Internal Displacement and Statelessness

2012 ◽  
Vol 4 (4) ◽  
pp. 475-504 ◽  
Author(s):  
Lindsey N. Kingston ◽  
Saheli Datta
Keyword(s):  
Large Scale ◽  
Physical Violence ◽  
Structural Violence ◽  
International Community ◽  
Internal Displacement ◽  
Internally Displaced ◽  
Global Responsibility ◽  
Cultural Violence ◽  
Starting Point ◽  
Large Populations

Norms of global responsibility have changed significantly since the 1948 Universal Declaration of Human Rights (UDHR), and today’s international community critically considers responsibilities within and beyond state borders, as evidenced by the adoption of the Responsibility to Protect (R2P) doctrine. From this starting point, protection must be extended to large populations susceptible to structural violence – social harms resulting from the pervasive and persistent impact of economic, political and cultural violence in societies. In order to show the potential of expanded conceptions of global responsibility, this article proceeds as follows: First, a discussion of the evolving concepts of responsibility outlines a shift in thinking about sovereignty that creates a multilayered system of responsibility. This section defines key concepts and highlights an ‘unbundled R2P’ framework for approaching structural violence. Second, an overview of two vulnerable populations – internally displaced persons (IDPs) and the stateless – illustrates that large-scale cases of state abuse and neglect are not limited to acts of physical violence, and that pervasive structural violence requires further attention from the international community. Lastly, recommendations are provided for expanding the scope of global responsibility in order to assist the internally displaced and the stateless. These recommendations address who is responsible, when global responsibility is warranted, and how such responsibility should be implemented.

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