Document Detail

Holocentric chromosomes in meiosis. II. The modes of orientation and segregation of a trivalent.
MedLine Citation:
PMID:  16823618     Owner:  NLM     Status:  MEDLINE    
The modes of orientation and segregation of the sex chromosome trivalent X1X2Y in male meiosis of Cacopsylla mali (Psylloidea, Homoptera) were analysed. Males with an X1X2Y sex chromosome system coexist with males displaying a neo-XY system in populations of this species. The fusion chromosome resulting in the formation of a trivalent in meiosis originates from the fusion of an autosome with the neo-Y chromosome. In the majority of metaphase I cells (92.4%) the X1X2Y trivalent showed co-orientation; X1 and X2 chromosomes oriented towards one pole whereas the Y oriented towards the opposite pole. In the rest of the cells (7.6%) the trivalent with subterminal chiasmata was oriented parallel to the equatorial plane. From this orientation the trivalent produced triple chromatids joined together by undivided telomeric parts of chromosomes and hence by sister chromatid cohesion at anaphase I. In the majority of metaphase II cells the orientation of triple chromatids suggested the production of unbalanced gametes. However, in a small number of cells (1.7%) the trivalent showed co-orientation of X1X2 with Y. Both the first division and second division co-orientations, or 94.1% of divisions as a whole, were estimated to yield balanced gametes, containing either X1 and X2 chromosomes or Y chromosome. It was concluded that, since the triple chromatid contained undivided telomere regions at metaphase II, which divided at anaphase II, the orientation of the trivalent with its longitudinal axis parallel to the equatorial plane in metaphase I also represents co-orientation and results in pre-reduction. The existence of post-reductional behaviour of holocentric bivalents and multivalents is discussed.
S Nokkala; V G Kuznetsova; A Maryanska-Nadachowska; C Nokkala
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2006-07-12
Journal Detail:
Title:  Chromosome research : an international journal on the molecular, supramolecular and evolutionary aspects of chromosome biology     Volume:  14     ISSN:  0967-3849     ISO Abbreviation:  Chromosome Res.     Publication Date:  2006  
Date Detail:
Created Date:  2006-07-06     Completed Date:  2006-10-30     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  9313452     Medline TA:  Chromosome Res     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  559-65     Citation Subset:  IM    
Laboratory of Genetics, Department of Biology, University of Turku, FIN-20014, Turku, Finland.
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MeSH Terms
Chromosome Pairing
Chromosome Segregation*
Hemiptera / genetics*
Meiosis / genetics*
Polymorphism, Genetic
Sex Chromosomes / physiology*
X Chromosome / physiology

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