Chromosome Research

, Volume 14, Issue 2, pp 139–150 | Cite as

An XX/XY sex microchromosome system in a freshwater turtle, Chelodina longicollis (Testudines: Chelidae) with genetic sex determination

  • Tariq Ezaz
  • Nicole Valenzuela
  • Frank Grützner
  • Ikuo Miura
  • Arthur Georges
  • Russell L. Burke
  • Jennifer A. Marshall Graves
Article

Abstract

Heteromorphic sex chromosomes are rare in turtles, having been described in only four species. Like many turtle species, the Australian freshwater turtle Chelodina longicollis has genetic sex determination, but no distinguishable (heteromorphic) sex chromosomes were identified in a previous karyotyping study. We used comparative genomic hybridization (CGH) to show that C. longicollis has an XX/XY system of chromosomal sex determination, involving a pair of microchromosomes. C-banding and reverse fluorescent staining also distinguished microchromosomes with different banding patterns in males and females in ∼70% cells examined. GTG-banding did not reveal any heteromorphic chromosomes, and no replication asynchrony on the X or Y microchromosomes was observed using replication banding. We conclude that there is a very small sequence difference between X and Y chromosomes in this species, a difference that is consistently detectable only by high-resolution molecular cytogenetic techniques, such as CGH. This is the first time a pair of microchromosomes has been identified as the sex chromosomes in a turtle species.

Key words

CGH Chelodina longicollis comparative genomic hybridization eastern snake-necked turtle microchromosomes sex chromosomes 

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Copyright information

© Springer 2006

Authors and Affiliations

  • Tariq Ezaz
    • 1
  • Nicole Valenzuela
    • 2
  • Frank Grützner
    • 1
  • Ikuo Miura
    • 3
  • Arthur Georges
    • 4
  • Russell L. Burke
    • 5
  • Jennifer A. Marshall Graves
    • 1
  1. 1.Comparative Genomics Group, Research School of Biological SciencesThe Australian National University CanberraAustralia
  2. 2.Department of Ecology, Evolution, and Organismal BiologyIowa State UniversityAmesUSA
  3. 3.Institute for Amphibian Biology, Graduate School of ScienceHiroshima UniversityHiroshimaJapan
  4. 4.Institute for Applied EcologyUniversity of CanberraCanberraAustralia
  5. 5.Department of BiologyHofstra UniversityHempsteadUSA

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