Preferential involvement of chromosomes no. 8 and no. 21 in acute leukemia and preleukemia.
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Chromosome analyses were performed by a direct method on bone marrow cells of 147 patients with acute leukemia and preleukemia; in 53 chromosomally abnormal cell lines were found. Chromosome abnormalities due to structural alterations were observed in 48% of the aneuploid patients. Using the ASG banding technique, the exact identification of the abnormal chromosomes was successfully made in 22 aneuploid patients. Even though variability between patients existed in the chromosome changes; the nonrandom occurrence of some chromosome abnormalities was revealed, involving most frequently chromosomes No. 8 and No. 21. Abnormalities of chromosome No. 22 were not encountered, contrasting sharply with the frequent involvement of this chromosome in chronic myelogenous leukemia. The significance of the preferential involvement of No. 8 and No. 21 chromosomes is discussed in relation to leukemogenesis. (+info)
Chromosomal banding patterns in acute nonlymphocytic leukemia.
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Bone marrow chromosomes obtained from 50 of 55 consecutive adult patients with acute nonlymphocytic leukemia were analyzed with quinacrine fluorescence. Twenty-five patients showed a normal karyotype and 25 an abnormal karyotype on the initial samples available for analysis. Among the 25 patients with abnormalities, the marrow cells contained 48 chromosomes in one case, 47 in two, 46 in ten, 45 in nine, 43 in two, and 42 chromosomes in one case. Seven of the ten patients with 46 chromosomes had abnormalities, primarily balanced translocations, that were not detected with the standard Giemsa stains. The analysis of all of the data available revealed the presence of nonrandom chromosome changes such as the addition of No. 8, the loss of No. 7, and a gain or loss of one No. 21. the most frequent structural rearrangement was the translocation between the long arm of No. 8 and No. 21, which may also be associated with the loss of a sex chromosome. Chromosomal abnormalities decreased or disappeared during remission; the same abnormality recurred in relapse. Chemotherapy did not appear to produce a stable clone of aberrant cells. Evolution of the karyotype occurred in eight patients, in five of whom an additional No. 8 was observed. This pattern of chromosomal evolution in patients with acute leukemia was very similar to that observed in patients with chronic myelogenous leukemia in the blast phase. (+info)
A novel sequence-based approach to localize translocation breakpoints identifies the molecular basis of a t(4;22).
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Low copy repeats (LCRs) located in 22q11.2, especially LCR-B, are susceptible to rearrangements associated with several relatively common constitutional disorders. These include DiGeorge syndrome, Velocardiofacial syndrome, Cat-eye syndrome and recurrent translocations of 22q11 including the constitutional t(11;22) and t(17;22). The presence of palindromic AT-rich repeats (PATRRs) within LCR-B of 22q11.2, as well as within the 11q23 and 17q11 regions, has suggested a palindrome-mediated, stem-loop mechanism for the generation of such recurring constitutional 22q11.2 translocations. The mechanism responsible for non-recurrent 22q11.2 rearrangements is presently unknown due to the extensive effort required for breakpoint cloning. Thus, we have developed a novel fluorescence in-situ hybridization and primed in-situ hybridization (PRINS) approach and rapidly localized the breakpoint of a non-recurrent 22q11.2 translocation, a t(4;22). Multiple primer pairs were designed from the sequence of a 200 kb, chromosome 4, breakpoint-spanning BAC to generate PRINS probes. Amplification of adjacent primer pairs, labeled in two colors, allowed us to narrow the 4q35.1 breakpoint to a 6.7 kb clonable region. Application of our improved PRINS protocol facilitated fine-mapping the translocation breakpoints within 4q35.1 and 22q11.2, and permitted rapid cloning and analysis of translocation junction fragments. To confirm the PRINS localization results, PCR mapping of t(4;22) somatic cell hybrid DNA was employed. Analysis of the breakpoints demonstrates the presence of a 554 bp palindromic sequence at the chromosome 4 breakpoint and a 22q11.2 location within the same PATRR as the recurrent t(11;22) and t(17;22). The sequence of this breakpoint further suggests that a stem-loop secondary structure mechanism is responsible for the formation of other, non-recurrent translocations involving LCR-B of 22q11.2. (+info)
Cytogenetic darkroom magic: now you see them, now you don't.
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Customary procedures used to determine chromosomal inheritance do not disclose many of the chromosomal polymorphisms known to be present, resulting in uninformative families. The sequential printing of individual chromosomes presented here is a technique that has increased the number of informative families in our studies. This technique has revealed previously unseen heritable chromosome differences and allowed the designation of parental origin. (+info)
Reciprocal translocation, 4q-; 21p+, giving rise to Down's syndrome.
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A reciprocal translocation is described, t(4;21)(q27;p11), which occurs in a balanced carrier mother and her Down's syndrome child, 47,XX,t(4q-;21p+),+21. A review is presented of Down's syndrome associated with reciprocal translations involving chromosome No. 21. (+info)
The repair of X-ray induced chromosomal damage in trisomy 2-and normal diploid lymphocytes.
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The frequency of chromosomal aberrations produced by X-rays is greater in lymphocytes cultured from trisomy 21 patients (Down's syndrome) than from normal diploid donors. This increase, which can be detected by a micronucleus assay for chromosomal damage, was postulated by us to result from a defect in the rejoining system which repairs chromosomal breaks. The postulated defect would result in a longer rejoining time, therapy permitting more movement of broken ends and thus enhancing the frequency of exchanges. To test this possibility, the time required for the rejoining (repair) of chromosome breaks was measured in lymphocytes from five Down's syndrome (four trisomy 21 and one D/G translocation partial trisomy 21) donors, from a monosomy 21 donor, and from five diploid donors. The rejoining time was reduced in the Down's syndrome lymphocytes in comparison to the normal diploid and monosomy 21 lymphocytes. Thus the repair of chromosome breaks, far from being defective as evidenced by a longer rejoining time in Down's syndrome cells, occurred more rapidly than in normal cells. A mechanism is proposed by which reduced rejoining times would increase aberration frequencies as a consequence of competition between a (hypothetical) error-free repair system and the error-prone repair system that generates chromosomal aberrations. We suggest that the alteration in the rejoining of chromosomal aberrations may underlie the increased susceptibility of people with Down's syndrome to leukemia. (+info)
A giant short arm of no. 21 chromosome in mother of 21/21 translocation mongol.
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An extreme variation of the short arm of no. 21 chromosome in the mother of a 21/21 translocation mongol is described. The possible relation between the very long short arm of chromosome no. 21 in the mother and a centric fusion type of translocation mongolism in the offspring is discussed. (+info)
Abnormal chromosome 22 and recurrence of trisomy-22 syndrome.
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Trisomy-22 was confirmed with both Q- and G-banding in two sibs. Growth and mental retardation plus various dysmorphic features of this syndrome are described and compared with previous reports. Cytogenetic studies reveal a morphologically atypical No. 22 in cells of the phenotypically normal mother (46,XX) and in both affected children. The variant G chromosome is identified as No. 22 by Q- and G-banding and is interpreted as a product of a pericentric inversion on the basis of general length, arm ratio (1.4), and anomalous satellite association frequency. Repeated nondisjunction for No. 22 is considered to have resulted from asynapsis caused by interference of an inversion loop configuration which, though short, comprised a major part of chromosome 22. (+info)