Showing papers on "Chromosome 21 published in 1971"

Presumed trisomy for the short arm of chromosome No. 9 not due to inherited translocation.

Abstract: 4 patients trisomic for the short arm of a chromosome No. 9 due to segregation of paternal translocations were described recently by Rethore and associates. In this context, we report on a retarded child, in whom the examination of lymphocyte and fibroblast metaphases revealed the existence of an additional small acrocentric marker chromosome. Cytogenetic data do not exclude the possibility of the marker to be derived from a chromosome No. 9 which exhibits, in the father, a more conspicuous secondary constriction than usual. A breakage event at this site and subsequent non-disjunction of the centric fragment (i.e. chromosome 9 short arm) during paternal gametogenesis could have given rise to the child's chromosomal constitution.

Autoradiographic studies of the human Y chromosome.

Abstract: An autoradiographic analysis (using continuous labeling with tritiated thymidine) was made on 317 cells from four normal males. The labeling pattern of the Y chromosome was compared to the first and the last chromosomes to complete replication as well as to G21–22. The Y chromosome was never found to be the last chromosome in the cell to complete replication. Instead, it completed DNA synthesis relatively early (usually among the first 10 chromosomes) but had a distinctively heavy label during the earliest stages of late-S. In 51% of those cells with one labeled G+Y chromosome, a G21–22 was labeled and the Y was not.—It was concluded, therefore, that the human Y chromosome is not a “late-replicating” chromosome but terminates replication earlier than most of the autosomes. In addition, the Y chromosome cannot be distinguished from the G chromosomes on the basis of a consistent and differential labeling pattern.

Study of a patient with apparent monosomy 21 owing to translocation: 45,XX,21-,t(18q+).

Abstract: A five-year-old girl with mild mental retardation and dyschondrosteosis was found to have 45 chromosomes A G (21-22) chromosome was missing The parents were chromosomally normal Measurements confirmed the presence of an unusually long chromosome No 17 or 18 in the girl’s karyotypes Late labeling with 3H-thymidine and autoradiography showed it to be No 18 By quinacrine fluoromicroscopy the apparently missing G chromosome proved to be No 21 Thus, the apparent autosomal monosomy was the result of a de novo 18/21 translocation with loss of the short arm and centromere of No 21 and of material from the long arms of No 18 or No 21 or both equivalent to two thirds of a G long arm Although no evidence was found for deletion of a genetic marker, heterozygosity at five gene loci (MNSs, Jk, Hp, PGM, and AcP) excluded their deletion We suggest that other instances of apparent autosomal monosomy may on careful study be found to be the result of similarly subtle chromosome rearrangements

Chromosomal abnormality in a phenotypically and clinically normal dog

Abstract: A seven-month-old black female setter-retriever cross was found to have a modal chromosome number of 77 and an apparent centric fusion of two autosomes. Extensive clinical examinations were performed,

Recombination in the X chromosome of Drosophila melanogaster females heterozygous for two autosomal translocations

Abstract: X chromosome recombination was measured in females carrying two 2; 3-translocations. Total X chromosome recombination values varied according to the amount of structural heterozygosity between the two translocations. The results support the hypothesis that the observed effects of autosomal translocation homozygosity on recombination in the X chromosome are due to homozygosity for position effects of the translocation breakpoints and are not due to chromosome discontinuity.