Karyotypic abnormality of the X chromosome is rare in mutant HPRT-lymphocyte clones |
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Authors: | P Muir Y Osborne A A Morley D R Turner |
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Institution: | Department of Haematology, Flinders Medical Centre, Bedford Park, South Australia. |
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Abstract: | Lymphocyte clones mutated at the hypoxanthine-guanine phosphoribosyl-transferase (HPRT) locus on the X chromosome were studied by synchronization and G banding to determine the proportion of mutant clones having visible karyotypic change. 47 spontaneously mutant clones, 17 mutant clones induced by X-irradiation and 33 wild-type clones were studied. All clones were karyotypically normal except for 1 clone induced by X-irradiation in which an interstitial deletion of the short arm of the X chromosome had been inserted into the long arm of the same chromosome between q23 and q24; this change may have been coincidental or may have resulted in a position effect mutation. It was concluded that the great majority of mutations were not associated with a visible chromosome abnormality. This conclusion complements molecular studies which suggest that gene changes at the HPRT locus in HPRT- mutants generally extend over segments of DNA too small to be resolved by karyotypic analysis. |
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