RESUMO
Genetic polymorphism has been demonstrated in man for many characteristics including blood groups, serum proteins, tissue enzymes, and hemoglobins. A class of chromosomal polymorphism involving constitutive heterochromatin has now been found. Through the use of a special technique that permits visualization of heterochromatin, seven heterochromatin variants have been found among four individuals. These results suggest a very high frequency of variability of heterochromatin in the population.
Assuntos
Heterocromatina , Polimorfismo Genético , Cromossomos Humanos 1-3 , Cromossomos Humanos 13-15 , Cromossomos Humanos 16-18 , Cromossomos Humanos 19-20 , Cromossomos Humanos 21-22 e Y , Cromossomos Humanos 6-12 e X , DNA , Humanos , Linfócitos , Métodos , Desnaturação de Ácido Nucleico , Renaturação de Ácido NucleicoAssuntos
Éter/farmacologia , Etil-Éteres/farmacologia , Halotano/farmacologia , Ativação Linfocitária/efeitos dos fármacos , Linfócitos/efeitos dos fármacos , Adulto , Idoso , Células Cultivadas , DNA/biossíntese , Feminino , Humanos , Cariotipagem , Masculino , Pessoa de Meia-Idade , Mitose/efeitos dos fármacos , Procedimentos Cirúrgicos OperatóriosRESUMO
An analysis of the inherited pattern of C-band heterochromatin has been made in five pedigrees containing a total of 33 offspring that were available for analysis. The majority of variants were found to be inherited; however, at least seven of the 99 variants were not present in either parent, and an additional seven differed from the parental variant by either a morphological change or the appearance of mosaicism. It is believed that the polymorphism of human constitutive heterochromatin arises from a mismatching of the repetitive DNA sequences contained in these regions with subsequent unequal crossing over. Further, the observed mosaic patterns provide suggestive evidence that such an event occurs in somatic cells as well as during meiosis.
Assuntos
Troca Genética , Heterocromatina , Polimorfismo Genético , Antígenos de Grupos Sanguíneos , Cromossomos/ultraestrutura , Feminino , Ligação Genética , Variação Genética , Humanos , Cariotipagem , Leucócitos/ultraestrutura , Masculino , Meiose , Mosaicismo , Linhagem , Fenótipo , Coloração e RotulagemRESUMO
A correlation between specific fragile sites and cancer breakpoints has been suggested raising the question of fragile site expression as a predisposing factor in the occurrence of cancer in some persons. Before addressing the question of increased fragility among patients at high risk for cancer, we analyzed the variability of aphidicolin-induced fragile sites among nine normal persons and also among repeated samples from three of these individuals. Considerable variation in both the frequency and location of these fragile sites was observed and the data strongly suggest the significant variation of 6 of the 16 selected sites to be primarily due to sampling differences. These findings indicate that the use of fragile sites as a screening tool for patients at high risk of cancer should be carefully monitored relative to the variation inherent in both culture and individual expression.