, Volume 103, Issue 7, pp 502–507 | Cite as

The karyotype of Alligator mississippiensis, and chromosomal mapping of the ZFY/X homologue, Zfc

  • Elizabeth M. A. Valleley
  • Christine J. Harrison
  • Yvonne Cook
  • Mark W. J. Ferguson
  • Paul T. Sharpe
Original Articles


Comparative mapping studies of X-linked genes in mammals have provided insights into the evolution of the X chromosome. Many reptiles including the American alligator, Alligator mississippiensis, do not appear to possess heteromorphic sex chromosomes, and sex is determined by the incubation temperature of the egg during embryonic development. Mapping of homologues of mammalian X-linked genes in reptiles could lead to a greater understanding of the evolution of vertebrate sex chromosomes. One of the genes used in the mammalian mapping studies was ZFX, an X-linked copy of the human ZFY gene which was originally isolated as a candidate for the mammalian testis-determining factor (TDF). ZFX is X-linked in eutherians, but maps to two autosomal locations in marsupials and monotremes, close to other genes associated with the eutherian X. The alligator homologue of the ZFY/ZFX genes, Zfc, has been isolated and described previously. A detailed karyotype of A. mississippiensis is presented, together with chromosomal in situ hybridisation data localising the Zfc gene to chromosome 3. Further chromosomal mapping studies using eutherian X-linked genes may reveal conserved chromosomal regions in the alligator that have become part of the eutherian X chromosome during evolution.


Mapping Study Incubation Temperature Comparative Mapping Chromosomal Mapping Hybridisation Data 
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  1. Bull JJ (1980) Sex determination in reptiles. Quart Rev Biol 55:1–21Google Scholar
  2. Bull JJ (1983) Evolution of sex determining mechanisms. Benjamin/Cummings, Menlo Park, CaliforniaGoogle Scholar
  3. Cohen MM, Gans C (1970) The chromosomes of the order Crocodilia. Cytogenetics 9:81–105Google Scholar
  4. Deeming DC, Ferguson MWJ (1991) Physiological effects of incubation temperature on embryonic development in reptiles and birds. In: Deeming DC, Ferguson MWJ (eds) Egg incubation: its effects on embryonic development in reptiles and birds. Cambridge University Press, Cambridge, UK, pp 147–172Google Scholar
  5. Ewens WJ, Griffiths RC, Ethier SN, Wilcox SA, Graves JAM (1992) Statistical analysis of in situ hybridisation data: derivation and use of the zmax test. Genomics 12:675–682Google Scholar
  6. Ferguson MWJ, Joanen T (1982) Temperature of egg incubation determines sex in Alligator mississippiensis. Nature 296: 850–853Google Scholar
  7. Ferguson MWJ, Joanen T (1983) Temperature-dependent sex determination in Alligator mississippiensis. J Zool Lond 200: 143–177Google Scholar
  8. Garson JA, van der Berghe JA, Kemshead JT (1987) Novel nonisotopic in situ hybridisation technique detects small (1 kb) unique sequences in routinely G-banded human chromosomes: fine mapping of N-myc and β-NGF genes. Nucleic Acids Res 15:4761–4770Google Scholar
  9. Graves JAM, Schmidt MM (1992) Mammalian sex chromosomes: design or accident? Curr Opin Gen Dev 2:890–891Google Scholar
  10. Graves JAM, Watson JM (1991) Mammalian sex chromosomes: evolution of organisation and function. Chromosoma 101: 63–68Google Scholar
  11. King M (1977) The evolution of sex chromosomes in lizards. In: Calaly J, Tyndale-Biscoe H (eds) Evolution and reproduction. Australian Academy Science, Canberra, pp 55–60Google Scholar
  12. King M, Honeycutt R, Contreras N (1986) Chromosomal repatterning in crocodiles: C, G and N-banding and the in situ hybridisation of 18S and 26S rRNA cistrons. Genetica 70: 191–201Google Scholar
  13. Lloyd SL, Sargent CA, Chalmers J, Lim E, Habeebu SSM, Affara NA (1991) An X-linked zinc finger gene mapping to Xq21.1–q21.3 closely related to ZFX and ZFY: possible origins from a common ancestral gene. Nucleic Acids Res 19:4835–4841Google Scholar
  14. Ohno S (1967) Sex chromosomes and sex-linked genes. Springer-Verlag, BerlinGoogle Scholar
  15. Olmo E (1986) Animal cytogenetics 4. Chordata 3. A. Reptilia. Gebrüder Borntraeger, BerlinGoogle Scholar
  16. Page DC, Mosher R, Simpson EM, Fisher EMC, Mardon G, Pollack J, McGillivray B, de la Chapelle A, Brown LG (1987) The sex determining region of the human Y chromosome encodes a finger protein. Cell 51:1091–1104Google Scholar
  17. Page DC, Fisher EMC, McGillivray B, Brown LG (1990) Additional deletion in the sex determining region of human Y chromosome resolves paradox of X,t (Y;22) female. Nature 346:279–281Google Scholar
  18. Schneider-Gädicke A, Beer-Romero P, Brown LG, Mardon G, Luoh S-W, Page DC (1989) Putative transcription activator with alternative isoforms encoded by the human ZFX gene. Nature 342:708–711Google Scholar
  19. Seabright M (1971) A rapid banding technique for human chromosomes. Lancet II:971–2Google Scholar
  20. Sinclair AH, Foster JW, Spencer JA, Page DC, Palmer M, Goodfellow PN, Graver JAM (1988) Sequences homologous to ZFY, a candidate human sex determining gene, are autosomal in marsupials. Nature 336:780–783Google Scholar
  21. Spencer JA, Sinclair AH, Watson JM, Graves JAM (1991a) Genes on the short arm of the human X chromosome are not shared with the marsupial X. Genomics 11:339–345Google Scholar
  22. Spencer JA, Watson JM, Graves JAM (1991b) The X chromosome of marsupials shares a highly conserved region with eutherians. Genomics 9:598–604Google Scholar
  23. Valleley EMA (1993) The molecular analysis of ZFY-related genes in the American alligator. Ph.D. thesis, University of Manchester, Manchester, UKGoogle Scholar
  24. Valleley EMA, Müller U, Ferguson MWJ, Sharpe PT (1992) Cloning and expression analysis of two ZFY-related zinc finger genes from Alligator mississippiensis, a species with temperature-dependent sex determination. Gene 119:221–228Google Scholar
  25. Watson JM, Spencer JA, Riggs AD, Graves JAM (1990) The X chromosome of monotremes shares a highly conserved region with the eutherian and marsupial X chromosome despite the absence of X chromosome inactivation. Proc Nat Acad Sci USA 87:7125–7129Google Scholar
  26. Watson JM, Frost C, Spencer JA, Graver JAM (1993) Sequences homologous to the human X- and Y-borne zinc finger protein genes (ZFX/X) are autosomal in monotreme mammals. Genomics 15:317–322Google Scholar

Copyright information

© Springer-Verlag 1994

Authors and Affiliations

  • Elizabeth M. A. Valleley
    • 1
  • Christine J. Harrison
    • 2
  • Yvonne Cook
    • 2
  • Mark W. J. Ferguson
    • 1
  • Paul T. Sharpe
    • 3
  1. 1.School of Biological Sciences, Stopford BuildingUniversity of ManchesterManchesterUK
  2. 2.Patorson Institute for Cancer ResearchChristie Hospital NHS TrustManchesterUK
  3. 3.Department of Craniofacial DevelopmentUMDS, Guy's HospitalLondonUK

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