Frequency of qh+ chromosomal variants in a) radioexposed, b) Down syndrome and c) control subjects.

"Paranormal" variants of human chromosomes, devoid of phenotypical effects (since what appears to vary is heterochromatic, non-genic DNA) are known to be heritable. Some very large variants (especially the qh+ variants on chromosomes 1 and possibly 16 and Y) were reported to be associated with increased reproductive pathology (sterility, fetal wastage, chromosomal aberrations). These variants are currently assessed by the C-band techniques; very large C-bands correspond to morphological alterations (elongation or deformation) of the chromosome. A study of qh+ morphological variants of chromosomes 1, 9 and 16 in 40 professionally radioexposed subjects, in 40 Down-syndrome patients and in 40 controls is reported, indicating that the frequency of each variant is lowest among controls, intermediate among professionally radioexposed subjects and highest among Down-syndrome patients. These findings, if confirmed, suggest a possible use of the qh+ variants as heritable indicators of chromosomal damage.

[Incidence of the 9qh+ variant in subjects with occupational exposure to radiation and in cases of reproductive pathology]. / Incidenza della variante 9qh+ in soggetti professionalmente radioesposti ed in casi di patologia reproduttiva.

The frequency of the 9qh+ variant was fond to be significantly increased (as compared to controls) in the following classes of subjects: R)professionally radioexposed individuals; P)patients with chromosomal aberrations; PP)parents of P; Cs)sterile or pluriabortive couples. While the increase of 9qh+ in P and PP individuals was already known, the findings in professionally radioexposed individuals and sterile or pluriabortive couples appear to be relatively new. Occurrence of 9qh+ might prove to be a useful indicator of chromosomal damage, while confirmation of these findings would entail stringent limitation of professional and diagnostic radioexposure.

[Incidence of the qh+ varients in the karyotype of subjects occupationally exposed to ionizing radiations]. / Incidenza delle varianti qh+ nel cariotipo di soggetti esposti professionalmente a radiazioni ionizzanti.

The "qh+" variants in the human karyotype are generally held to be inherited and devoid of phenotypical effects, although more frequent in families with cases of chromosomal aberrations. The finding of an even higher frequency of apparent mosaicism for 9qh+ in the karyotype of individuals professionally exposed to radiation supports the hypothesis that the variant may be mutagen-induced, possibly reflecting a "first hit" in chromosomal damage. Further studies are under way to verify the hypothesis, in view of a possible use as an indicator of radiation damage and/or risk factor in genetic counseling.