Nom du corpus

Corpus Systématique Animale

Titre du document

Sex chromosomes of the chinchilla: Allocycly and duplication sequence in somatic cells and behavior in meiosis

Lien vers le document
Springer (journals)
Langue(s) du document
Type de document
Nom du fichier dans la ressource
  • Michael Galton 1,2
  • Kurt Benirschke 1,2
  • Susumu Ohno 1,2
  • 1) Department of Pathology, Dartmouth Medical School, Hanover, N. H., USA
  • 2) Department of Biology, City of Hope Medical Center, Duarte, California, USA

The X-chromosome of the chinchilla is the largest member of the complement. Since its area equals approximately 9% of that of the haploid autosome set, it may represent a “duplicate-type X-chromosome”, in contrast to the “original-type” in which the ratio X:autosomes ranges from 5 to 6.5%. Unlike other known species with the “duplicate-type X-chromosome”, the chinchilla possesses a very small Y-chromosome. It was inferred from the allocyclic behavior and asynchronous replication pattern of the sex chromosomes in somatic cells that one X-chromosome in the female and the male X-chromosome manifest a single genetically active region: the presumed active segment is inserted in the longer arm adjacent to the centromere. The remainder of these X-chromosomes, the entire second X-chromosome in the female and the Y-chromosome displayed positive heteropycnosis in mitotic prophase and completed DNA synthesis prior to mitosis later than any other elements: this cytologic behavior was held to reflect genetic inertness. The existence of genetic inactivation of much of the “duplicate-type” X-chromosome mass of the chinchilla supports the hypothesis that a constant optimal ratio between the functional portion of the X-chromosomes and the autosomes is maintained in mammals despite a wide range of relative sizes of the X-chromosomes. In female meiosis there is a free exchange of chiasmata between the X-chromosomes at first meiotic metaphase. In the male, however, the association between the large X- and small Y-chromosomes during meiosis is invariably end-to-end, denoting the absence of synapsis. This contrasts with the occurrence of side-by-side pairing of the XY-bivalent in other mammals possessing the “duplicate-type X-chromosome” but in which the Y-chromosome is correspondingly large.

Catégories Science-Metrix
  • 1 - health sciences
  • 2 - biomedical research
  • 3 - developmental biology
Catégories INIST
  • 1 - sciences appliquees, technologies et medecines
  • 2 - sciences biologiques et medicales
  • 3 - sciences biologiques fondamentales et appliquees. psychologie
Catégories Scopus
  • 1 - Health Sciences ; 2 - Medicine ; 3 - Genetics(clinical)
  • 1 - Life Sciences ; 2 - Biochemistry, Genetics and Molecular Biology ; 3 - Genetics
Catégories WoS
  • 1 - science ; 2 - genetics & heredity
  • 1 - science ; 2 - biochemistry & molecular biology
Identifiant ISTEX


Année de publication
Présence de XML structuré
Version PDF
Score qualité du texte
  • Mammiferes
Type de publication
Powered by Lodex 9.3.8