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| Predicate | Object |
|---|---|
| rdf:type | |
| lifeskim:mentions | |
| pubmed:issue |
1
|
| pubmed:dateCreated |
1976-4-30
|
| pubmed:abstractText |
After conjugation in the ciliated protozoan, Oxytricha, polytene chromosomes are formed during the development of a macronucleus from a micronucleus. Here we report a microscopic study of these chromosomes and an analysis of their DNA. The polytene chromosomes of Oxytricha bear a strong morphological resemblance to the polytene chromosomes of the Dipteran salivary gland. The nucleus of a developing macronuclear anlage contains 120 +/- 2 polytene chromosomes and each chromosome has an average of 81 hands; a total of about 10,000 bands per nucleus. At a later stage in development, the number of bands per chromosome is reduced by a factor of four, presumably due to fusion of adjacent bands. The polytene chromosomes then break up into their constituent bands, each of which is encased in a vesicle. There are about 2,700 vesicles per nucleus.--During the growth of polytene chromosomes, there is a change in the relative proportion of sequences in the DNA. The DNA from polytene nuclei has a buoyant density of 1.695 g/cc, significantly lighter than the density of the original micronuclear DNA (1.698 G/cc to 1.702 g/cc). We interpret this buoyant density change to be the result of differential replication of DNA sequences during polytene chromosome growth. A second change in DNA composition occurs after the polytene stage of development, shown by a shift in buoyant density to 1.701 g/cc in the DNA of the mature macronucleus. During this second process, the molecular weight of the DNA is reduced from greater than 50 x 10(6) daltons to about 2 x 10(6) daltons.
|
| pubmed:language |
eng
|
| pubmed:journal | |
| pubmed:citationSubset |
IM
|
| pubmed:chemical | |
| pubmed:status |
MEDLINE
|
| pubmed:month |
Jan
|
| pubmed:issn |
0009-5915
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| pubmed:author | |
| pubmed:issnType |
Print
|
| pubmed:day |
27
|
| pubmed:volume |
54
|
| pubmed:owner |
NLM
|
| pubmed:authorsComplete |
Y
|
| pubmed:pagination |
1-13
|
| pubmed:dateRevised |
2006-11-15
|
| pubmed:meshHeading |
pubmed-meshheading:813980-Animals,
pubmed-meshheading:813980-Centrifugation, Density Gradient,
pubmed-meshheading:813980-Chromosomes,
pubmed-meshheading:813980-Chromosomes, Human, 6-12 and X,
pubmed-meshheading:813980-Ciliophora,
pubmed-meshheading:813980-Conjugation, Genetic,
pubmed-meshheading:813980-DNA,
pubmed-meshheading:813980-DNA, Satellite,
pubmed-meshheading:813980-DNA Replication,
pubmed-meshheading:813980-Humans
|
| pubmed:year |
1976
|
| pubmed:articleTitle |
Polytene chromosomes of Oxytricha: biochemical and morphological changes during macronuclear development in a ciliated protozoan.
|
| pubmed:publicationType |
Journal Article,
Research Support, U.S. Gov't, P.H.S.,
Research Support, U.S. Gov't, Non-P.H.S.
|