Showing papers on "Ring chromosome published in 1973"

Ring chromosome 7 with variable phenotypic expression

Abstract: Two males with apparently identical rings of chromosome 7 and very different phenotypic features are presented. Patient 1 is severely retarded, has short stature, microcephaly, craniosynostosis, unilateral proptosis, ptosis, and microcornea, small phallus, first-degree hypospadias, and undescended testes. Patient 2 is of normal intelligence, and his only abnormalities are short stature and a small head. Study of lymphocytes at metaphase showed the same proportion of cells with the ring, 46, XY, r(7), and those without a ring, 45, XY,-7, in each case. Quinacrine fluorescence and Giemsa banding techniques showed all the bands of chromosome 7 to be present, suggesting little material missing as a result of ring formation. A similar degree of instability of the ring in each case was indicated by the frequency of abnormal cells at anaphase and telophase.

Developmental Abnormalities Associated with a Ring Chromosome 6

Abstract: A clinical and cytogenetic report is made of a patient with microcephaly, peculiar facies, and retardation of physical and mental development, who possesses a karyotype containing a ring chromosome No. 6 identified by Q-staining with quinacrine mustard. This is the first report of a ring autosome in the C group to be identified. Comparison with other patients reported as having C-group autosomal rings failed to reveal many common phenotypic characteristics.

Points of exchange in a human no. 5 ring chromosome.

Abstract: A 46, XYq+, r(B) karyotype was observed in a four-month-old boy with cri du chat syndrome. The ring was identified as a No. 5 on the basis of both G-staining and quinacrine fluorescence. The break points were located at bands 5ρl5 and 5q35, i.e., his karyotype was 46, XYq+ , r(5)(pl5q35). The loss of chromosome material was estimated to be about 5.5% of a normal No. 5 chromosome. The father also had a Yq+ chromosome.

Monozygotic Twins with Ring Chromosome 22

Abstract: Mentally retarded and monozygous twin sisters, with little physical abnormality, are described. Each twin carried a small ring chromosome, identified as a number 22.

A child with a 21-ring chromosome, 45XX,21minus-46,XX,21r investigated with the banding technique.

Abstract: Chromosomal analysis of lymphocytes and fibroblasts in a slightly retarded 7-month-old female infant with some minor malformations showed a mosaicism 45,XX,G-/46,XX,Gr. The ring chromosome was identified as No. 21 by banding technique.

Instability of the maize B chromosome.

Abstract: The B 9 chromosome of maize exhibits a very ordered type of instability at the second pollen mitosis, when nondisjunction may reach a level of 95%. Much less commonly the chromosome is unstable during early development of the kernel. Instability in the kernel produces recessive sectors in either the endosperm or the sporophyte, reflecting the absence of dominant markers carried by the B 9. The causes of B 9 loss in the endosperm and the sporophyte were investigated for the two observable classes of sectoring: fractional loss (single event) and multiple loss (mosaic pattern). The fractional class represents isochromosome formation by the B 9 (Carlson, 1970, 1971). Data presented here suggest that the isochromosome is a by-product of telocentric formation at the second pollen mitosis, and does not arise directly from the B 9 chromosome. The chromosomal basis for the mosaic pattern of B 9 loss is not completely known. However, one class of mosaic kernels displays a heritable instability of the B 9 chromosome which apparently results from ring chromosome formation by the B 9. The time of origin of the ring B 9 chromosome is prior to the second pollen mitosis, since the unstable chromosome generated in the male parent is transmitted to both the endosperm and the sporophyte. Finally, a genetic factor controlling B 9 stability in the developing endosperm has been found. A single plant (1818-1), crossed as a female parent to a B 9-containing stock, induced a mosaic pattern of B 9 loss in the endosperm at a very high rate. The characteristics of this plant are being investigated.

Ring-1 chromosome, microcephalic dwarfism, and acute myeloid leukemia.

Abstract: A 9-year-old girl suffered from severe dwarfism, mental retardation, and a ring chromosome No. 1. She developed anemia characterized by multinuclearity of the marrow erythroblasts, and finally died with acute myeloid leukemia. The leukemic cells had a distinctive, pseudodiploid karyotype lacking the ring chromosome. The clinical features are compared with those of two other children with ring chromosome No. 1. The hematological abnormalities are presumed to be related to the development of the leukemic clone.

Hemophilia B in a phenotypically normal girl with XX (ring) XO mosaicism.

Abstract: Severe factor IX deficiency (Christmas disease) in a phenotypically normal girl prompted a cytogenetic study of the proband and her parents which showed, in the patient, a karyotype with 46 chromosomes (XX ring) and a karyotype comprised of 45 chromosomes with a single X chromosome (45XO). The parents were cytogenetically normal. The activity of factor IX in the patient was markedly abnormal (less than 1%). It is suggested that XX (ring)XO mosaicism permitted expression of the abnormal X-linked gene.

Changes in the structure of B (A) chromosomes in maize.

Abstract: A class of mosaic endospersm involving the marker SuI was observed among the progeny of individuals hyperploid for the chromosome B4 and genetically analyzed. The exceptional individuals showing mosaic endosperm were found when the hyperploid material was used as pollen source. While in some cases mosaicism was limited to the endosperm tissue, with no apparent consequences in the embryo, in others the mosaicism was transmitted to the progeny, which showed changes in the structure of the B4 chromosome, with the formation of unstable chromosomes whose genetic behaviour was similar to that of ring chromosomes. This interpretation was cytologically confirmed. In other cases the B4 chromosome analyzed in mosaic endosperm individuals underwent altered transmission frequencies or loss, suggesting that its original structure had been modified by breakage-fusion-bridge cycles. The changes in this chromosome revealed by the mosaic phenotype are discussed in relation to the original structure of the B chromosome and the B4 hyperploid condition.

A ring D chromosome in association with Down's syndrome-like phenotype

Abstract: The case of a ten-years-old mentally retarded girl with Down's syndrome-like features whose chromosome analysis revealed an unusual mosaicism including 10% mitosis with a ring chromosome replacing a D chromosome is reported. The clinical features of the patient were considered similar to those described by Jacobsen (1966) and Emberger et al. (1971) who interpreted the ring chromosome present in their patients as being chromosome 15.