A case of pericentric inversion chromosome 9 with an associated personality disorder is reported. There is justification for a more widespread cytogenetic screening of psychiatric disorders of this type.
Sixty‐two translations were isolated in the M1 generation of gamma‐irradiated plus sodium‐azide treated populations of safflower (Carthamus tinctorus L.). Most of the simple translocations were induced at 30 and 45 kR, whereas the high dose (60 kR) produced complex interchanges which failed to produce seed. Sodium azide alone induced no chromosomal interchanges. The pollen sterility of the interchange heterozygotes ranged from 1 to 99.6% with an average of 53.76%; 10 of the translocation heterozygotes showed pollen sterility comparable to the standard normal. The interchange heterozygotes at metaphase I had characteristic chain and ring multivalents, mostly quadrivalents. Chain configurations were in excess of the rings in most of the translocations. Alternate orientation of the quadrivalents was most common.
The polymorphisms of constitutive heterochromatin regions, present on chromosomes 1, 9, 16 and Y, are inherited in a Mendelian fashion. The C-band heteromorphism has been reported to be associated with various types of cancer. Heterochromatin is considered to play a role in protecting genome against the mutagens. Changes in the quantity and proportion of the different types of satellite DNA might increase the genetic susceptibility in people with heterochromatic variations, which in turn cause chromosome instability and predispose the individual to cancer. We report a case of bilateral retinoblastoma with complete absence of pericentromeric heterochromatin on one of the chromosomes number 9. A similar deficiency of pericentromeric heterochromatin on chromosome number 9 and 16 has been reported in a phenotypically normal individual and a Down syndrome case, respectively. This deficiency was found to be inherited from the father in all the three cases. Complete absence of pericentromeric heterochromatin of chromosome 9 is not being reported in association with cancer syndromes. Further studies are necessary to understand the role of this factor in normals and in those with cancer susceptibility, specially with retinoblastoma and the paternal origin of this deficiency.
An efficient squash technique for resolving the somatic chromosomes of safflower (Carthamus tinctorius L.) was developed. It permitted the detailed analysis of the karyotype. The 12 pairs of chromosomes were classified and numbered from 1 to 12 on the basis of their descending order of length, centromere position and presence of satellites. The absolute chromosome length varied from 3.52 to 2.05 μ, the average being 2.90 μ. The arm ratios ranged from 1.25 to 4.50. The centromere was mostly median to submedian, being subterminal in two pairs of chromosomes. There were three pairs of satellite‐chromosomes, the nucleolus being organized by the short arm. A karyotype formula has been suggested.
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