Electronic Resource
Oxford, UK
:
Blackwell Publishing Ltd
The @journal of eukaryotic microbiology
19 (1972), S. 0
ISSN:
1550-7408
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
The hypotrichous ciliate Keronopsis rubra has ∼10 micronuclei and ∼100 small macronuclei. DNA synthesis proceeds synchronously in all macronuclei in the 2nd half of the cell cycle which takes about 24 hr at room temperature. A G2 phase is virtually absent, each nucleus dividing as soon as the replication band has passed over it. The micronuclear S phase falls within macronuclear G1 and is followed by immediate division. Comparative cytophotometric measurements of Feulgen-stained preparations indicate that the DNA content of G1 macronuclei is scattered widely in a skewed normal distribution, with a peak corresponding to the DNA content of a G1 micronucleus. Measurements of dividing macronuclei indicate unequal distribution of DNA between daughter nuclei and lead to the conclusion that the units of assortment must be smaller than whole genomes unless the micronucleus is polyploid. After conjugation, a large macronuclear anlage with threads resembling split prophase chromosomes is formed. The threads condense and pass singly into the cytoplasm where they are thought to give rise to the numerous small macronuclei of the vegetative cells.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1550-7408.1972.tb03555.x
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