ABSTRACT
A case of monosomy 22 diagnosed prenatally is reported. During pregnancy, ultrasonic observations already revealed several cardiac malformations of the fetus in the 25th week. Following counselling, the pregnancy was terminated. Fetal autopsy revealed several abnormalities associated with DiGeorge syndrome.
Subject(s)
Chromosomes, Human, Pair 22 , DiGeorge Syndrome/diagnostic imaging , Monosomy , Ultrasonography, Prenatal , Adult , DiGeorge Syndrome/genetics , Female , Fetal Diseases/diagnostic imaging , Fetal Diseases/genetics , Humans , PregnancyABSTRACT
A meiotic analysis has been carried out on male mice heterozygous for one of two inversions in Chromosome 2, In(2)5Rk and In(2)2H, as well as on double heterozygotes for these two overlapping inversions. Electron microscopic observation of synaptonemal complexes revealed that heterosynapsis had occurred in a large number of spermatocytes, producing a small number of cells with an inversion loop. Heterozygous carriers of a single inversion loop reproduced quite normally, whereas doubly heterozygous carriers of a double loop showed a reduction in spermatogenesis. These data shed new light on the role of inversions in speciation.
Subject(s)
Chromosome Inversion , Chromosome Mapping , Heterozygote , Infertility, Male/genetics , Animals , Chromosome Banding , Crosses, Genetic , Female , Male , Mice , Mice, Inbred C57BL , Mice, Inbred Strains , Spermatocytes/cytology , Spermatocytes/pathology , Synaptonemal Complex/geneticsABSTRACT
We present two prenatal cases of trisomy 9 mosaicism, both of which presented intrauterine growth retardation (IUGR) and other abnormal ultrasound findings. In case A, mosaicism was found in amniotic fluid cell cultures, of which 65 per cent were trisomic cells, on average. In case B, trisomic cells were present in amniotic fluid cell cultures (12 per cent) but none were found in fetal cord blood. After autopsy, cytogenetic findings were confirmed in different tissue cultures. It is concluded that echographic indicators are a very useful tool for a correct prenatal diagnostic interpretation of trisomy 9. Suspected trisomy 9 mosaicism always requires further investigation and fetal cord blood cytogenetic analysis may not be considered as providing an accurate diagnosis of fetal trisomy 9.
Subject(s)
Abnormalities, Multiple/genetics , Amniocentesis , Chromosomes, Human, Pair 9 , Mosaicism , Trisomy , Abnormalities, Multiple/diagnostic imaging , Adult , Facial Bones/abnormalities , Female , Fetal Growth Retardation/diagnostic imaging , Fetal Growth Retardation/genetics , Humans , Pregnancy , Pregnancy Trimester, Second , Skull/abnormalities , Stomach/abnormalities , Ultrasonography, PrenatalABSTRACT
The nature and origin of two de novo small marker chromosomes found at prenatal diagnosis were determined by fluorescence in situ hybridization using chromosome centromere-specific probes and chromosome-specific plasmid libraries. One marker was found in a mosaic state and was shown to be an i(18p). The second marker was characterized as an inv dup(22). We conclude that molecular cytogenetic analysis contributes to the identification of marker chromosomes and therefore facilitates genetic counselling and decision-making for the parents.
Subject(s)
Genetic Markers , Prenatal Diagnosis/methods , Adult , Amniocentesis , Chromosomes, Human, Pair 18 , Chromosomes, Human, Pair 22 , Diagnosis, Differential , Female , Fluorescent Dyes , Humans , In Situ Hybridization/methods , Intellectual Disability/genetics , Karyotyping , Middle Aged , Pregnancy , Pregnancy Trimester, SecondABSTRACT
Silver-stained synaptonemal complexes in surface-spread pachytene nuclei from an oligospermic man, heterozygous for a reciprocal translocation involving an acrocentric chromosome, were analyzed by electron microscopy. Contrary to the classically expected configuration, nonhomologous pairing was observed with asymmetrical association of the lateral elements of the nonhomologous arms of the quadrivalents. A possible role of heterosynapsis in germ cell conservation is discussed.
Subject(s)
Heterozygote , Synaptonemal Complex/genetics , Translocation, Genetic , Adult , Chromosomes/metabolism , Chromosomes/ultrastructure , Humans , Infertility, Male/genetics , Male , Meiosis , Microscopy, ElectronABSTRACT
Silver-stained synaptonemal complexes in surface-spread pachytene nuclei from a man, heterozygous for a reciprocal translocation, were analysed by electron microscopy. Contrary to the classically expected cross-shaped configuration, extensive non-homologous pairings were observed with asymmetrical association in the lateral elements of the non-homologous arms of the quadrivalents. A possible role of the heterosynapsis in reproductive failure is discussed.
Subject(s)
Chromosomes, Human, Pair 4 , Chromosomes, Human, Pair 6 , Synaptonemal Complex , Translocation, Genetic , Adult , Chromosome Banding , Genetic Carrier Screening , Humans , Karyotyping , Male , Microscopy, Electron , Testis/ultrastructureABSTRACT
The examination of synaptic data and localization of chromosomal breakpoints in a review of human pericentric inversions suggest that synaptic and recombination behaviour in rearranged chromosomes during meiosis can be predicted by determining the subband in which the breakpoint is located. According to this hypothesis, it can be postulated that loops in pericentric inversions are routinely formed only in cases when both breaks occur in G-light bands, with the genetic consequences of crossing-over. In other cases, heterosynapsis is accomplished without previous homosynapsis, thereby minimizing the production of unbalanced gametes.
