title: Anaphase lagging mainly explains chromosomal mosaicism in human preimplantation embryos.
abstract: BACKGROUND
  Cleavage stage embryos as well as postimplantation embryos have been studied extensively over the years. However, our knowledge with respect to the chromosomal constitution of human embryos at the blastocyst stage is still rudimentary.
  
  
  METHODS
  In the present paper, a large series of human blastocysts was examined by means of fluorescent in situ hybridization (FISH).
  
  
  RESULTS
  It was found that only one in four blastocysts (25%) displayed a normal chromosomal pattern. We defined a group of blastocysts (26%) displaying a simple mosaic chromosome pattern (different cell lines resulting from one chromosomal error), an about equally large group of blastocysts (31%) displaying a complex mosaic chromosome pattern, and a smaller group of blastocysts (11%) showing a chaotic chromosome distribution pattern. Six per cent of all blastocysts analysed could not be assigned one of the previously mentioned chromosomal patterns.
  
  
  CONCLUSIONS
  Anaphase lagging appeared to be the major mechanism through which human embryos acquire a mosaic chromosome pattern during preimplantation development to the blastocyst stage.
authors.affiliation: Research Institute Growth & Development (GROW), Maastricht University and Department of Obstetrics & Gynaecology, Academic Hospital Maastricht, The Netherlands. eco@sgyn.azm.nl
authors.forename: Edith
authors.initials: E
authors.lastname: Coonen
authors.forename: Josien G
authors.initials: JG
authors.lastname: Derhaag
authors.forename: John C M
authors.initials: JC
authors.lastname: Dumoulin
authors.forename: Lucie C P
authors.initials: LC
authors.lastname: van Wissen
authors.forename: Marijke
authors.initials: M
authors.lastname: Bras
authors.forename: Marij
authors.initials: M
authors.lastname: Janssen
authors.forename: Johannes L H
authors.initials: JL
authors.lastname: Evers
authors.forename: Joep P M
authors.initials: JP
authors.lastname: Geraedts
mesh_terms: D000705:Anaphase / Q000235:genetics*; D001755:Blastocyst / Q000648:ultrastructure*; D002877:Chromosomes, Human / Q000235:genetics*; D002970:Cleavage Stage, Ovum / Q000648:ultrastructure; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D007621:Karyotyping; D008297:Male; D009030:Mosaicism / Q000235:genetics*; D011247:Pregnancy; D020554:Sperm Injections, Intracytoplasmic