The mutation responsible for Huntington's disease (HD) is an elongated CAG repeat in the coding region of the IT15 gene. A PCR-based test with high sensitivity and accuracy is now available to identify asymptomatic gene carriers and patients. An inverse correlation between CAG copy number and age at disease onset has been found in a large number of affected individuals. The influence of the CAG repeat expansion on other phenotypic manifestations, especially specific psychiatric symptoms has not been studied intensively. In order to elucidate this situation we investigated the relation between CAG copy number and distinct psychiatric phenotypes found in 79 HD-patients. None of the four differentiated categories (personality change, psychosis, depression, and nonspecific alterations) showed significant differences in respect to size of the CAG expansion. In addition, no influence of individual sex on psychiatric presentation could be found. On the other hand in patients with personality changes maternal transmission was significantly more frequent compared with all other groups. Therefore we suggest that clinical severity of psychiatric features in HD is not directly dependent on the size of the dynamic mutation involved. The complex pathogenetic mechanisms leading to psychiatric alterations are still unknown and thus genotyping does not provide information about expected psychiatric symptoms in HD gene carriers.

In this report we present a method to determine sex chromosomal aneuploidies by duplex polymerase chain reaction with sufficient precision to distinguish between one, two and more copies of X and Y sequences. We coamplified an autosomal gene segment (exon 33 of neurofibromatosis type I gene on chromosome 17) as an internal standard for our sequence of interest (AMXY) on X and Y chromosomes. By using this standard as a reference for two gene copies we could visually estimate the relative gene dosage for the X-, and Y-specific AMXY sequences in the DNA sample under consideration. We have evaluated this method in normal males and females and in patients with known sex chromosomal aneuploidies and have found it to be a reliable and quick tool for detection of numerical sex chromosomal abnormalities.

Two thirds of the patients with Down's syndrome are born by women below 35 years of age. An extension of invasive prenatal diagnosis to these women is problematical due to the operative risks and the relatively high costs. Therefore, non-invasive screening methods are sought, apt to identify groups at high risk. Biochemical screening methods applied at 16 weeks of pregnancy (triple test) and the new first trimester tests are discussed. Ultrasound screening at 10 to 12 weeks is dealt with in more detail. A large fluid cushion over most of the back was documented not only in most cases of trisomy 21 but in trisomies 18 and 13 and in Turner's syndrome as well. Only few chromosomally normal fetuses with the same pecularity were observed. Systematic first trimester screening for nuchal fluid accumulation seems to be a recommendable method for the detection of chromosome anomalies. It compares favourably with current methods of maternal serum screening performed at 16-18 weeks which require a manyfold higher number of invasive procedures.

To establish preclinical DNA-diagnosis of neurofibromatosis type 1 (NF1) in familial cases we have investigated 38 families segregating for the disease. The families were tested with 6 polymorphic DNA markers from the chromosome region 17p11.1-q11.2. Two-thirds of the families were informative for flanking markers. An informative situation was achieved for 33 out of 40 individuals at risk (i.e. first degree relatives): 30 cases were diagnosed as noncarriers of the mutated gene, and three clinically normal individuals (including an adult and two children aged three and six respectively) were found to carry the risk haplotype. The remaining 7 persons at risk could not be typed unequivocally due to non-informative markers or recombination events. In 5 families with healthy grandparents the origin of the mutation could be traced back to the grandfather's germ cells. Despite the recent cloning and initial characterization of parts of NF1 gene, studies using linked and eventually intragenic DNA markers will continue to be of great value for genetic counselling. Such analyses allow highly accurate preclinical and prenatal diagnosis in close relatives of familial cases.

To establish preclinical DNA-diagnosis of neurofibromatosis type 1 (NF1) in familial cases we have investigated 38 families segregating for the disease. The families were tested with 6 polymorphic DNA markers from the chromsome region 17p11.1-q11.2. Two-thirds of the families were informative for flanking markers. An informative situation was achieved for 33 out of 40 individuals at risk (i.e. first degree relatives): 30 cases were diagnosed as non-carriers of the mutated gene, and three clinically normal individuals (including an adult and two children aged three and six respectively) were found to carry the risk haplotype. The remaining 7 persons at risk could not be typed unequivocally due to non-informative markers or recombination events. In 5 families with healthy grandparents the origin of the mutation could be traced back to the grandfather's germ cells. Despite the recent cloning and initial characterization of parts of NF1 gene, studies using linked and eventually intragenic DNA markers will continue to be of great value for genetic counselling. Such analyses allow highly accurate preclinical and prenatal diagnosis in close relatives of familial cases.

High-molecular-weight DNA was recovered postmortem in sufficient quantities from various human organ tissues as well as from blood, although not all organs were equally well suitable. Good DNA stability was found in brain cortex, lymph nodes and psoas muscle over a period of three weeks postmortem. Spleen and kidney showed good DNA stability up to five days postmortem but after longer periods, rapid degradation was observed. Yields of DNA from blood were not consistent because of the non homogeneity of samples. Blood clots were rich with DNA. Generally, the amount of degraded DNA correlated directly with the duration of the postmortem period. However in some cases, DNA degradation was already prominent after a short period. Case histories showed that high environmental temperature at the site of death and/or infectious diseases prior to death were the main factors for rapid autolysis. Gradual disappearance to complete loss of the long fragments (15–23 kb) was observed in DNA fingerprinting using the minisatellite probe 33.15. No extra-bands were noted, thus excluding erroneous conclusions. However, evidentiary value of older samples was lower.

The discovery of linked DNA markers permits presymptomatic and prenatal diagnosis of autosomal-dominant Huntington's disease. However, family members born at 50% risk can find out if they have inherited the mutant gene only if family analyses are possible. Many individuals at risk lack a sufficient number of living relatives for presymptomatic testing. However, prenatal exclusion testing in pregnancy can be offered to most probands. In four case reports we demonstrate the first clinical use of these markers for genetic counselling in Switzerland. The method was used for both presymptomatic testing and prenatal diagnosis. Prenatal exclusion testing is described in one family. The general practitioner should be informed of the potentialities of DNA technology, since competent advice to his patients and follow-up of positive probands are part of his duties.

Zusammenfassung In den Schweizerischen Laboratorien von Basel, Bern, Genf, Lausanne, Locarno und Zürich wurden von 1971 bis 1983 insgesamt 19'872 pränatale genetische Untersuchungen durchgeführt. Die Häufigkeit der Untersuchungen aus den verschiedenen Indikationen und die Zahlen der dabei ermittelten Anomalien werden dokumentiert. Bei den 12'485 aus Altersindikation (35 J. und älter) vorgenommenen Untersuchungen wurden 241 Chromosomenanomalien diagnostiziert, davon 125 Trisomien 21. Bei 5'225 Proben von Frauen unter 35 fanden sich nur 7 Trisomien 21. In 93 Prozent der Fälle war die Prävention des Down-Syndroms die Hauptmotivation der Schwangeren. Rund 42 Prozent der über 35-jährigen machten in den letzten Jahren in der Schweiz Gebrauch vom Angebot der Amniocentese. Grosse Fortschritte sind bei der Ultraschalldiagnostik fetaler Missbildungen zu verzeichnen. Im weiteren befasst sich der Uebersichtsartikel mit den Entwicklungen auf dem Gebiet der pränatalen Diagnostik im ersten Trimester sowie mit der DNA-Diagnostik monogener Erbkrankheiten an Chorionbiopsien.

If a ring 21, originating from breaks close to the telomere of 21q and anywhere in 21p, replaces a normal 21, it may be associated with an apparently normal phenotype. An apparently normal mother and son were ascertained by a prenatal chromosome study. A second mother, with a ring 21 but without gross anomalies, is short of stature, has epilepsy, and has a low normal intelligence. Her daughter is a mosaic: 46, XX/47, XX, + r(21) and has the Down's syndrome. None of these four persons was found to have mitoses with more than one ring 21 or with rings of double size.

Some twenty cases of dispermic chimeras with the karyotype 46,XX/46,XY, discovered because of gonadal dysplasias or a true hermaphroditism, have been reported. This is a report of a phenotypically normal man with 46,XX/46,XY chimerism in whom a prepubertal finding of positive X-chromatin was interpreted as Klinefelter syndrome. The diagnosis was revised 11 years later when the family doctor, who doubted the earlier diagnosis because of the patient's normal-sized testes, sent him to an outpatient clinic. The young man was 23 years old, athletic (74kg, 180cm), with normal body proportions, normal sexual hair distribution, normal libido and potency, normal endocrine parameters, and a normal spermiogram. The karyotype revealed an XX/XY mosaic in a proportion of 1:2. An identical set of maternal markers (Q- and C-banding) was present in male and female cells. Differences were found with respect to two paternal markers. Furthermore, blood, serum, and red cell enzyme groups in five systems showed two phenotypes, again with duality of paternal origin. It is concluded that a positive X-chromatin in prepuperty, especially in the absence of supporting clinical features, must be followed by a karyotype study.

Medical geneticists invest a great part of their resources towards the prevention of the birth of children with trisomy 21. Since, however, it will never be possible to monitor all pregnancies and, moreover, rejection of prenatal diagnosis on ethical grounds is widespread, this paper discusses the possibilities of lightening the burden on relatives of children with Down's syndrome. The contrast of the negative example shown by Switzerland with positive experiences achieved in Denmark serves to show that highly beneficial results can be obtained by humanizing the school system. This holds true not only for the severely retarded and their families, but also for children with minor learning disabilities as well. Such changes in the school system, when correctly applied, are of advantage to more gifted students as well.

AbstractBilateral cleft lip and cleft palate can be diagnosed by ultrasonography prior to 20 weeks of pregnancy. The anomaly produces an abnormal facial profile and, on cross‐section, the clefts in the maxilla are demonstrable. The method is illustrated by sonograms from a fetus in which the defect was diagnosed before trisomy 13 became known by karyotyping.

In human interphase nuclei containing Yq isochromosomes or two Y chromosomes, there are conspicuous somatic pairings between the brightly fluorescing Y-heterochromatin regions. These somatic pairings cannot be demonstrated in metaphases from conventional cell cultures because they are disrupted at the mitotic prophase. However, in lymphocytes cultivated in a medium containing distamycin A, the somatic pairing between Y-heterochromatin is preserved to metaphase. The present findings are compared with earlier observations of somatically paired heterochromatin. An explanation for the highly disparate frequency of somatic pairing between the Y-heterochromatin regions in Yq isochromosomes and YY chromosomes is proposed.

Eleven patients with the so-called Cat Eye syndrome are reported including a more detailed description of the original cases reported by Schnid and Fraccaro. All cases had, in addition to a normal karyotype, a small extra G-like chromosome which appeared to be an isochromosome for the juxtacentromeric region (pter→q11) of an acrocentric chromosome. None were mosaics. Clinical findings and further cytogenetic studies in a few cases suggest that these markers probably derive from a No. 22 chromosome.