Eleven populations of five Avena species were analysed for meiotic characters including chiasma frequency and distribution as well as chromosomal association and segregation. Plants of a single population of A. eriantha showed the presence of 2n = 14 (diploid) and 2n = 4x = 28 chromosome number. Populations of A. barbata and A. wiestii possessed n = 14, while populations of A. sterilis ssp. lud...

Seven previous cases of ring chromosome 7 (r(7)) have been reported in association with minor anomalies with and without mental retardation [Zackai and Breg, 1973; Nakano and Miyamoto, 1977; DeLozier et al., 1982; Barros et al., 1986; Kohyama et al., 1988; Koiffmann et al., 19901. All of the reported patients had evidence of mosaicism with the r(7) line predominating and low frequencies of doub...

A girl presented at 6 weeks of age with failure to thrive and arching of the back. She had various dysmorphic features, hepatosplenomegaly, and developmental delay. The electroencephalogram and cranial ultrasound were abnormal, and a computed tomogram showed lissencephaly and apparent agenesis of the corpus callosum. Because of frequent aspiration she became oxygen dependent. She later develope...

SMC proteins are key components of large ring-shaped chromosomal protein complexes, such as cohesin and condensin. New evidence supports the idea that these rings topologically encircle DNA. Hints also emerge as to what it may take for DNA to enter the ring.

Chromosomal abnormality is one of the causal factors in the formation of the congenital heart defects. 65 patients (33 male and 32 female) with heart defects were referred for karyotyping and counseling. Chromosomal abnormalities were detected in 27 (41.5%) and 38 had a normal karyotype. Numerical abnormality was found in 21 (77.8%) and structural in 6 (22.2%), numerical was detected in 14 fema...

The severe phenotype of human females whose karyotype includes tiny ring X chromosomes has been attributed to the inability of the small ring X chromosome to inactivate. The XIST locus is expressed only from the inactive X chromosome, resides at the putative X inactivation center, and is considered a prime player in the initiation of mammalian X dosage compensation. Using PCR, Southern blot ana...

We report on a prenatal diagnosis of ring chromosome 15 in a fetus with left congenital diaphragmatic hernia (CDH) and severe intrauterine growth restriction (IUGR). A 31-year-old woman, gravida 2 para 1, was referred because of increased nuchal translucency at gestational age of 13 weeks. Comprehensive fetal ultrasound examination was performed at 19 weeks revealing an early onset IUGR, left C...

ING-SHAPED chromosomes provide an opportune situation for the analysis R of some aspects of chromosome mechanics. In particular, sister-strand crossing over eludes detection in rod chromosomes but its consequences in ring chromosomes are manifested by the formation of anaphase bridges. Thus RICCLIKTOCK (1938) and SCHWARTZ (1953) have presented cytological evidence for the occurrence of exchange...

A patient with a 14q32.3 terminal band deletion and cat cry is reported. Review of four other 14q32.3 deletion cases suggests the possible presence of a recognisable 14q32.3 terminal deletion syndrome, which is characterised by (1) apparently postnatal onset of small head size in comparison to body size, (2) high forehead with lateral hypertrichosis, (3) epicanthic folds, (4) broad nasal bridge...