title: Mosaic trisomy 13: understanding origin using SNP array.
abstract: BACKGROUND
  Trisomy 13 occurs in 1/10,000-20,000 live births, and mosaicism accounts for 5% of these cases. Phenotype and outcome of mosaic trisomy 13 are variable and poorly understood. Microsatellite analyses of trisomy 13 have indicated the high incidence of maternal meiotic origin and reduced recombination, but no study has focused on mosaic trisomy 13 in live born patients.
  
  
  RESULTS
  Single-nucleotide polymorphism (SNP) array, fluorescence in situ hybridisation and bioinformatics analyses were performed in three cases of mosaic trisomy 13. Two cases of complete mosaic trisomy 13 originated from meiosis I non-disjunction followed by trisomic rescue; one had crossovers resulting in segmental uniparental disomy in the disomic line, and one had no crossover. Mosaicism for partial trisomy 13 in the third complex case either arose from meiosis II non-disjunction without crossover or in early mitosis followed by anaphase lags. The extra chromosome 13 was maternal in origin in all three cases. Mosaicism percentage calculated from B allele frequencies ranged from 30 to 50.
  
  
  CONCLUSIONS
  Genotypes and copy number information provided by SNP array allow determination of parental origin and uniparental disomy status and direct quantification of mosaicism. Such information may lead to a better understanding of mechanisms underlying mosaic aneuploidies and the observed phenotypic variability and better prediction of recurrent risk.
authors.affiliation: Institute of Genetic Medicine, Johns Hopkins Medical Institutions, Baltimore, MD 21287, USA.
authors.forename: Natini
authors.initials: N
authors.lastname: Jinawath
authors.forename: Regina
authors.initials: R
authors.lastname: Zambrano
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Wohler
authors.forename: Maria K
authors.initials: MK
authors.lastname: Palmquist
authors.forename: Julie
authors.initials: J
authors.lastname: Hoover-Fong
authors.forename: Ada
authors.initials: A
authors.lastname: Hamosh
authors.forename: Denise A S
authors.initials: DA
authors.lastname: Batista
mesh_terms: D000328:Adult; D025063:Chromosome Disorders / Q000235:genetics; D002882:Chromosomes, Human, Pair 13 / Q000235:genetics; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008540:Meiosis / Q000235:genetics; D008938:Mitosis / Q000235:genetics; D009030:Mosaicism; D009630:Nondisjunction, Genetic / Q000235:genetics; D020411:Oligonucleotide Array Sequence Analysis; D010641:Phenotype; D020641:Polymorphism, Single Nucleotide / Q000235:genetics*; D014314:Trisomy / Q000235:genetics; D000073839:Trisomy 13 Syndrome