Recent work suggests that an autosomal dominant gene for schizophrenia may be located on the 5q11-q13 region of chromosome 5 (refs 1 and 2): a report of schizophrenia associated with trisomy 5q11-q13 in two members of a family of Chinese origin prompted the discovery of linkage with markers p105-599Ha and p105-153Ra in five Icelandic and two English schizophrenic families. The strongest linkage was observed when the phenotype was broadly defined to include minor psychiatric diagnoses not traditionally considered part of the schizophrenia spectrum. By contrast, no evidence was found of linkage in a single multiplex Swedish schizophrenic pedigree. To determine whether these conflicting results arise from genetic and/or uncertainties in defining the schizophrenic phenotype, we examined fifteen Scottish schizophrenic families with restriction fragment length polymorphisms that span this region. We found no evidence for linkage, regardless of how broadly or narrowly the schizophrenic phenotype is defined, and conclude that a susceptibility locus, whose presence awaits confirmation, on the proximal portion of the long arm of chromosome 5 can be responsible for only a minority of cases of familial schizophrenia.
Restriction endonuclease digestion of genomic DNA generates DNA fragments of unique size, dependent upon the particular base sequence. Following fractionation by agarose gel electrophoresis, repetitive DNA can be visualized as distinct bands in stained gels and the restriction fragment length of such bands used as diagnostic characters. Restriction fragment length differences were detected between species within the genera Trichinella, Caenorhabditis, Romanomermis, Steinernema (syn. Neoaplectana) and Meloidogyne. This technique provides a new tool for the taxonomist, which is independent of phenotypic variation and it enables the rapid and reliable separation of closely related species.
Molar diseases of the placenta is associated with cystic change in the villi. The cysts may be from 5-20+ mm in diameter. This disease has been described in association with triploid and diploid cell lines and with and without an accompanying embryo or fetus. It may be followed by malignant change and invasive chorio-carcinoma. In order to investigate the association between cell ploidy, embryonic development and subsequent malignancy, a detailed study of 30 conceptuses with molar disease was made, with the accompanying maternal history and follow-up. The cell ploidy was determined by measurement of nuclei by a cytoscan light microscope connected to a computer program as has been previously described. Diploid cell lines were not found with embryonic or fetal development. Triploid cell lines were always associated with an embryo or fetus. Triploidy is not associated with hyperplastic changes in the trophoblast. These results are presented and discussed.
The region around the twitcher gene, unc-22, flanked by unc-43 on the left and by unc-31 on the right, has been intensively studied in our laboratory over the period of the last 8 years. In this paper we describe the identification and isolation of probes specific for several restriction fragment length differences (RFLDs) which lie within this region. Many RFLDs in Caenorhabditis elegans are caused by the insertion of a transposable element, Tc1. The method we used involved the isolation of Tc1-containing genomic fragments. These were recovered from a lambda gt 10 library of DNA from a specially constructed genetic strain containing the unc-43 to unc-31 interval from the BO strain and the rest of the genome from N2. Because the BO strain is rich in Tc1 insertion sites and the N2 strain has few, the majority of Tc1-bearing genomic fragments in the constructed strain were derived from the unc-22 region. Of nine such Tc1-bearing genomic fragments isolated, six were found which mapped within the region of interest. The 350 kilobases of genomic sequences isolated as a result of these studies are being used to study the molecular organization of this region. The method described here for Tc1 linkage selection is one that is rapid, general, and may be targeted to any genetically characterized region of the C. elegans genome.
Chromosomal analysis from aborted tissue has become an important diagnostic aid. However, the necessary cultures are frequently unsuccessful due to the condition of the aborted tissue. Polyploidy, in particular triploidy, in the conceptus is a common cause of early pregnancy loss and unlike aneuploidy does not appear to be associated with an increased recurrence risk. The necessity to monitor a subsequent pregnancy with amniocentesis is therefore eliminated. Therefore, in cases where a chromosomal anomaly is probable, a fast simple method of identification of a polyploid karyotype would be valuable. In this presentation, we describe a method using a scanning light microscope and histologic tissue preparations. This method can accurately determine the ploidy of the aborted material in 5 days.
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