title: Within pair differences of human chromosome 9 C-bands associated with reproductive loss.
abstract: The size and position of the heterochromatic regions of chromosome 9 were examined in a group of women with histories of recurrent miscarriage and a control group of fertile women. Measurements were made on whole chromosomes (variability between chromosomes was taken to reflect differences in heterochromatin), and corrections for between-cell contraction were made by comparison with chromosome 7. Chromosomes were analysed in pairs and the following results were obtained: (1) The larger of the pairs of chromosomes of the test group were significantly larger than those of the control group: (2) The smaller of the pairs of chromosomes were the same in each group: (3) The differences between the chromosome pairs were significantly greater in the test than the control group: and (4) The sums of the homologous chromosomes were significantly greater in the test than in the control group. Independent assessment also showed that a significantly higher frequency of complete pericentric inversions of chromosome 9 was present in the test than the control group. These results are discussed in the light of two hypotheses: (1) The difference in the size of the homologous chromosomes is critical, and (2) the total heterochromatic content of a chromosome and/or cell is critical. Some evidence is presented to support each hypothesis, but the former is the more favoured by the data.
mesh_terms: D002503:Centromere / Q000648:ultrastructure; D002869:Chromosome Aberrations; D002871:Chromosome Banding; D002906:Chromosomes, Human, 6-12 and X / Q000648:ultrastructure*; D005260:Female; D006570:Heterochromatin / Q000648:ultrastructure; D006801:Humans; D007247:Infertility, Female / Q000235:genetics*
chemical_list: D006570:Heterochromatin