Document Detail

The X1X2Y sex chromosome system in the fish Hoplias malabaricus. II. Meiotic analyses.
MedLine Citation:
PMID:  9543017     Owner:  NLM     Status:  MEDLINE    
The neotropical fish Hoplias malabaricus shows diversified cytotypes and may represent a group of distinct species. One of these cytotypes is characterized by 2n = 40 and 2n = 39 chromosomes in females and males, respectively, with a multiple sex chromosome system of the X1X1X2X2/X1X2Y type. The Y, representing a large chromosome in male karyotype, is derived from a translocation event between two biarmed chromosomes: one of them similar to X1 chromosome (no. 6) and another one similar to X2 chromosome (probably no. 20). Meiotic data (standard and synaptonemal complexes analyses) show 18 bivalents and one characteristic trivalent in pachytene and metaphase I spermatocytes, as well as two kinds of metaphase II cells with 19 and 20 chromosomes. The trivalent is formed by the Y, X1 and X2 chromosomes and usually presents a complete pairing in pachytene. However, trivalents with partially or fully asynapsed segments are also observed. These segments are assumed to be non-homologous regions of the X1 and X2 chromosomes without correspondence with the Y chromosome, which can heterosynapse. This behaviour of the sex trivalent leading to a fully paired structure, taken together with the close frequencies of the two spermatocyte types at metaphase II, suggests a normal pattern for male H. malabaricus meiosis, representing a stabilized multiple sex chromosome system in this species.
L A Bertollo; C A Mestriner
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Chromosome research : an international journal on the molecular, supramolecular and evolutionary aspects of chromosome biology     Volume:  6     ISSN:  0967-3849     ISO Abbreviation:  Chromosome Res.     Publication Date:  1998 Feb 
Date Detail:
Created Date:  1998-05-14     Completed Date:  1998-05-14     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  9313452     Medline TA:  Chromosome Res     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  141-7     Citation Subset:  IM    
Departamento de Genética e Evolução, Universidade Federal de São Carlos, SP, Brazil.
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MeSH Terms
Fishes / genetics*
Spermatocytes / cytology
Synaptonemal Complex
X Chromosome* / genetics,  ultrastructure
Y Chromosome* / genetics,  ultrastructure

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