Ulla Gripenberg

The cytological behavior of a human ring-chromosome

A ring chromosome derived from group 17–18 was found in a mentally retarded girl. The ring shows considerable variability. With respect to the size the ring is enlarged in 9% of the cells. In 19% of the cells the ring is eliminated; in these cells the chromosome number is only 45. The elimination of the ring has been studied. There are cytological indications of two simultaneous mechanisms: lagging and destruction of complex unstable structures.

Size variation and orientation of the human Y chromosome

SummaryThe material consists of 84 metaphase plates from 17 individuals with clearly distinguishable Y chromosomes. The plates were obtained from leucocyte cultures. In making the preparations, exactly the same procedure was employed in all cases, including among other things, air-drying and light flaming.It was found that the size of the Y chromosome is subject to interindividual variation. The size of the Y chromosome has been expressed in relation to the mean length of the other small acrocentric chromosomes. The chromosomes have been tentatively classified into the following main groups:1. Y/G = 1.8; 2. Y/G =1.5; 3. Y/G is somewhat larger than G or 1.1, and 4. Y/G equals the mean of the small acrocentric chromosomes, or Y/G = 1. In the long Y chromosome two secondary constrictions have been observed.The location of the Y chromosome has been determined as peripheral or non-peripheral. The proband material has been divided into three main groups. The first comprises the individuals with a large Y chromosome (Y/G = 1.8). The second group includes individuals showing Downs syndrome and having 47 chromosomes, and the third comprises individuals with 46 chromosomes and possessing a Y/G sized 1 to 1.5. Preferential peripheral location of the Y chromosome has not been statistically verified in any one of these groups.

Mutagenicity and toxicity of amitrole. I. Drosophila tests

Amitrole was highly toxic at early larval stages of Drosophila (LD50 is 40 ppm in medium). Toxicity of amitrole was also revealed by prolongation of development time even at 10 ppm. However, no mutagenic effects of amitrole were observed either in the sex chromosome non-disjunction test (females reared on medium containing amitrole at 10 ppm) or in the sex-linked recessive lethal test (males reared on medium containing amitrole at 10 ppm).

Mutagenicity and toxicity of amitrole. II. Human lymphocyte culture tests

Effects of amitrole (3-amino-1,2,4-triazole) on human leucocytes in culture were investigated. Amitrole interfered with lymphoblast transformation and inhibited cell growth in concentrations of 0.2% w/v and higher. Selected metaphases were examined for the presence of chromosome and chromatid aberrations. No clastogenic effects were observed.

Mutagenicity and toxicity of amitrole. III. Microbial tests

Amitrole (3-amino-1,2,4-triazole) inhibits bacterial growth both in Escherichia coli and Salmonella typhimurium at a concentration of 0.5% in minimal medium. Repression of growth already occurs at a concentration of 0.1% of amitrole in this medium. In complete medium the bacteria tolerate concentrations of amitrole as high as 1.7-2.4% before growth ceases. Mutagenicity was tested by differential growth comparisons on E. coli strains W 3110 thy pol A1, defective in DNA polymerase I, and its revertant pol A+. Known mutagens (MMS, NTG, mitomycin C) were used as positive controls. Analogous negative results were also obtained in a revertant test when several trp mutant strains of Salmonella were used.

A D/F Translocation in a Case of Regular Trisomy 21 Down’s Syndrome

A girl aged 9 months with clinical symptoms of Down’s syndrome had 47 chromosomes in preparations from peripheral blood leucocytes. An unusual karyotype was found with abnormal distributions of chromosomes in the following groups: C:17, D:5, F:3 and G:6. The interpretation of the karyotype is based on the assumption that there is a simultaneous occurrence of trisomy in group G and a translocation between chromosomes of group D and F. The mechanism to which these deviations are attributable is discussed. A causal relationship between trisomy and translocation is suggested.

Down’s Syndrome

A chromosomal study was performed on 174 patients with Down’s syndrome, all inmates at an institution for the mentally retarded. Among them, 8 translocations, 1 double trisomy, 1 case of mosaicism and