Showing papers on "Ring chromosome published in 1969"

The effect of triated thymidine on sister chromatid exchange in a ring chromosome

Abstract: Peripheral lymphocytes from a human male heterozygous for a ring chromosome were cultured both in the presence and absence of tritiated thymidine. Analysis of colchicine-anaphase cells showed that incorporated triated thymidine induced a substantial increase in the frequency of dicentric ring chromosomes. Comparable levels of dicentrics in the first and second cell cycle following isotope incorporation indicated that dicentric induction is a dose (tritium)-independent process. The frequency of induced dicentrics, and hence of induced exchange between the sister ring chromatids, approximated the frequency of sister-chromatid exchange (determined autoradiographically) in rod chromosomes. This suggests, but does not prove, that sister-chromatid exchanges in rod chromosomes are radiation induced events.

IgA Deficiency Associated With Partial Deletion of Chromosome 18

Abstract: IN CONTRAST to the X chromosome, little is known about the autosomal loci for various genetic traits. Recently Gerald et al1 and Bloom et al 2 have presented suggestive evidence that the controlling formation of locus the α-chain of haptoglobin is situated on one end of a No. 13 chromosome. We have studied two patients with chromosome defects and dysgammaglobulinemia. One had a No. 18 ring chromosome, which is formed by breakage in both arms with reunion of the broken ends and loss of a variable amount of material distal to each break. The other had a partial deletion of the long arm of the same chromosome. In both patients IgA was not detectable, and, in one, the level of IgG was very low. These patients are the first recognized examples of dysgammaglobulinemia associated with a chromosomal deletion. Report of Cases Case 1.—A 3-year-old white boy was first admitted to

Cytogenetic and nuclear studies on A9 and B82 cells fused together by sendai virus: the early phase.

Abstract: A9 and B82 enzyme-deficient mutants of the L line of mouse cells were hybridized artificially in vitro. After exposure of the cells to the fusing agent (inactivated Sendai virus), cultures were grown in a selective medium with aminopterin, which allows the survival only of heterokaryons which contain both A and B nuclei. The chromosome make-up of the fused cells was then studied for an initial 3-month period under various conditions. Polykaryons with 2 or more nuclei were at first observed but, as the cultures progressed, only mononucleate cells (synkaryons) persisted. Most cells in mitosis showed the chromosomal set of one A and one B cell, with an average mode and chromosome make-up very similar to, but not exactly, the sum of the average s chromosome number of one A and one B nucleus (as cells). As a rule, the synkaryons contained three ‘dot-like’ chromosomes, two of which were probably derived from the A cell and one from the B cell. In the course of the 3-month study the relative frequency of the 2s cells and their average modal number varied little. However, an increasing number of 2s cells with abnormally shaped chromosomes, in particular new ring chromosomes, was noted. Some of the cells had a mode intermediate between the 2s number and the s number (hypo-2S cells). They were thought to represent new segregants, but they were scarce, and their frequency did not increase when established fused cells were removed from the selective medium and then grown for up to 3 weeks. Nuclear polymorphism was present in all cultures and certain cytological observations gave the impression that fractions of the genomes of fused cells could be rejected through nuclear fragmentation. Synkaryons resulting from cell fusion induced by Sendai virus showed a remarkably stable chromosomal constitution for the first 3 months of culture, and were endowed with striking reproductive fitness.

Ring chromosomes in two infants with congenital malformations.

Abstract: Ring chromosomes in association with congenital malformations have previously been reported in approximately 26 patients. The ring chromosome was apparently derived from one of the X chromosomes in 6 patients (Lindsten and Tillinger, 1962; Liiers, Struck, and Nevinny-Stickel, 1963; Hustinx and Stoelinga, 1964; Bain, Gauld, and Farquhar, 1965; Pfeiffer and Biichner, 1965; Bishop et al., 1966), and was assigned to the A group in one instance (Gordon and Cooke, 1964), and to the B group in another (Rohde and Tompkins, 1965). Three examples of C group ring chromosomes (Smith-White et al., 1963; Atkins et al., 1966a); 8 of the D group (Wang et al., 1962; Bain and Gauld, 1963; Turner, 1963; Reisman, Darnell, and Murphy, 1965; Adams, 1965; Teplitz et al., 1967; Sparkes, Carrel, and Wright, 1967; Gerald et al., 1967), 4 of the E group (Wang et al., 1962; Genest, Leclerc, and Auger, 1963; Lucas et al., 1963; Gropp, Jussen, and Ofteringer, 1964), and one of the G group (Hoefnagel, Schroeder, and Benirschke, 1967) have been reported. Two other infants with ring autosomes of unknown origin have also been described (Fisher, 1965; Atkins, Sceery, and Kennan, 1966b). This paper presents two examples of infants with ring chromosomes. In one instance the ring chromosome replaces a chromosome of the D group (13-15); the other is a mosaic with one line consisting of normal 46,XY plus a ring chromosome of unknown derivation. The latter case is rare, since, to our knowledge, only one other instance of a trisomic state in which one of the chromosomes is a ring has been reported (Atkins et al., 1966b).

Chromosome chromatid rearrangements resulting from the mitotic crossing-over between sister-chromatids in ring chromosomes of Creptis capillaris.

Abstract: All radiation-induced aberrations in dry seeds of Crepis capillaris are chromosome rearrangements. The main types of chromosome rearrangements in the above tests were asymmetrical and symmetrical exchanges, ring chromosomes and ring deletions. The majority of ring chromosomes is of a chromosomes type which brings about paired rings. Fig. 1 presents the mechanism of the production of the paired rings. In a number of cases the structure of rings proved to be quite unexpected. Among middle size rings single rings proved to occur in 18.8%, among microrings-1.9% cases. Somewhat fewer are presented by pairs of rings one inside the other. The large rings present complex figures made by tangled chromatids. Two rings make one due to mitotic crossing-over between sister-chromatids (Fig. 5). Double crossing-over would lead to the exchange of part of material between two independent rings or to one ring being thrust into the other due to different strand positions in two points of the exchange. Large rings is the provision of complicated exchanges.

Ring chromosome 18 (46, XX, 18r).

Abstract: Description of a new case of 46,XX,18r. Features which are similar to those seen in 18q- anomaly are dystrophy, microcephaly, epicanthic folds, strabism, digital whorl patterns and IgA deficiency.

Cytogenetics in mentally defective children anomalies: A controlled study with

Abstract: Chromosomal analysis was performed on 50 mentally defective children with three or more congenital anomalies, and chromosomal preparations were randomly coded for analysis. Four children had abnormal karyotypes: one was mosaic for an extra small ring chromosome, one had a 2-3 translocation, one was a clinically undiagnosed 18-trisomy and one had a partial deletion of the long arm of 18. No abnormalities were found in preparations from control subjects.