Cytogenetics of collared lemmings (Dicrostonyx groenlandicus) I. Meiotic behavior and evolution of the neo-XY sex-chromosome system

• Published in: Cytogenetic and Genome Research
• Main Authors: Berend, S.A., Hale, D.W., Engstrom, M.D., Greenbaum, I.F.
• Format: Article in Journal/Newspaper
• Language: English
• Published: S. Karger AG 1997
• Subjects: Dicrostonyx groenlandicus
• Online Access: http://dx.doi.org/10.1159/000134746; https://www.karger.com/Article/Pdf/134746

Electron-microscopic analysis of surface-spread synaptonemal complexes at pachynema and light-microscopic analysis of chromosomal configurations at diakinesis/metaphase I corroborate the hypothesized neo-XY derivation of the sex chromosomes of Dicrostonyx groenlandicus. Although an intact neo-XY pairing configuration was observed in a relatively small percentage of the pachytene cells in each individual, the high incidence of neo-XY bivalents at diakinesis/metaphase I suggests that the other observed pachytene configurations were artifacts of the physical stresses of the surface-spreading procedure. The very low frequency (0.6 %) of univalent neo-X and neo-Y chromosomes at diakinesis and metaphase I is attributable to consistent synapsis and recombination between their homologous autosomally derived segments. The resultant stability of the sex bivalent through metaphase I may have increased the efficacy of sex-chromosome segregation, and thereby played a mechanistic role in the evolutionary incorporation of the neo-XY sex-chromosome constitution in D. groenlαndicus.