Familial pericentric inversion of chromosome 18: behavioral abnormalities in patients heterozygous for either the dup(18p)/del(18q) or dup(18q)/del(18p) recombinant chromosome.

We describe a family in which the largest hitherto reported pericentric inversion of chromosome 18, inv(18)(p11.22q23), segregates. Individuals heterozygous for the nonrecombinant inversion were unaffected.

Subtelomeric familial translocation t(2;7)(q37;q35) leading to partial trisomy 7q35-->qter: molecular cytogenetic analysis and clinical phenotype in two generations.

Few patients with trisomy of the most distal region of chromosome 7q have been described. We report on a familial translocation t(2;7)(q37;q35) leading to trisomy 7q35-->7qter in a child and her paternal uncle and a minimal deletion of distal 2q as demonstrated by FISH with probes located in the chromosome 2q subtelomeric region. The clinical phenotype included macrocephaly and low-set ears, also found in other reported patients trisomic for the distal part of chromosome 7q.

Application of fluorescence in situ hybridization to the identification of different marker chromosomes.

Chromosome studies performed on lymphocyte culture of a baby with specific dysmorphism and congenital anomalies suggestive of trisomy 21 revealed a mosaicism: 46,XY,rea(21q21q) [25]/47,XY,rea(21q21q),+mar1[25]. The karyotype of the mother is normal, but the father's karyotype presents an supernumerary chromosome greater and different from the marker of his son: 47,XY,+mar2 (100%). The identification of the two marker chromosomes by standard cytogenetic techniques followed by molecular techniques is essential for the identification of the origin of these two chromosomes.

Fluorescent in-situ hybridization on human embryos showing cleavage arrest after freezing and thawing.

Our current freezing-thawing policy is to transfer only embryos that cleave further in the 24 h following thawing. The purpose of our study was to investigate the incidence of numerical abnormalities for chromosomes X, Y and 1 in blastomeres of human preimplantation embryos that survived cryopreservation but did not cleave further after thawing. A total of 63 embryos surviving a freezing-thawing cycle but not cleaving further within 24 h after thawing were screened.

Triple colour fluorescent in-situ hybridization for chromosomes X,Y and 1 on spare human embryos.

The potential for implantation of human embryos obtained by in-vitro fertilization is presumably determined to a large extent by their chromosomal constitution but cytogenetic analysis of preimplantation embryos has been hampered by a number of practical and technical problems. With the advent of fluorescent in-situ hybridization (FISH) a practical method for numerical chromosomal analysis has become available. A limited amount of data has been obtained with FISH on human embryos using probes binding to chromosomes X, Y, 16, 18 and 13/21 combined or for chromosomes X and Y or 1 and 17.