In a large survey of oeri and paracentric inversions, it could be demonstrated that, in human populations, some inversions are very recurrent. This may indicate that after breakage, the numbers of reassociations leading to inversion, within a given chromosome are limited. This may correspond to homologous deoxyribonucleic acid (DNA) sequences distributed along the chromosomes.
A quantitative study has been carried out of radiation induced chromosomal breakage and a test for radiation sensitivity developed.
The results obtained by studies performed during the previous contract indicated that chromosome rearrangements induced by ionizing radiations might not be random. The analyses of chromosome lesions were pursued in several conditions. In a large survey of oeri- and paracentric inversions, it could be demonstrated that, in human populations, some inversions are very recurrent. This may indicate that after breakage, the numbers of reassociations leading to inversion, within a given chromosome are limited. This may correspond to homologous DNA sequences distributed along the chromosomes.
A QUALITATIVE STUDY OF RADIATION INDUCED CHROMOSOMAL CHANGES IN DIFFERENT SPECIES.
CELL CULTURES WILL BE IRRADIATED WITH GAMMA-RAYS AND OTHER PARTICLES. INDUCED CHROMOSOMAL CHANGES WILL BE ANALYSED BY THE R BAND METHOD AND THE DISTRIBUTION OF BREAKAGE POINTS WILL BE STUDIED. A METHOD OF STATISTICAL ANALYSIS, DEVELOPED IN THE LABORATORY DURING THE PREVIOUS PROJECT WILL BE USED TO TEST FOR THE RISKS OF CHROMOSOMAL MUTAGENESIS.
APART FROM HUMANS, DIFFERENT SPECIES SELECTED FOR THEIR TYPICAL KARYOTYPES WILL BE ANALYSED IN ORDER TO DISCOVER WHETHER THE KINDS OF CHANGES WHICH OCCUR DEPEND ON THE SIZE, SHAPE OR NUMBER OF CHROMOSOMES.
THE TRANSMISSION OF THE CHROMOSOMAL CHANGES CELL DIVISION WILL BE STUDIED TO ESTIMATE INDIRECTLY THE RISK OF TRANSMISSION OF CHROMOSOMAL ABERRATIONS TO DESCENDANTS OF IRRADIATED SUBJECTS.IN ORDER TO DO THIS, THE RELATIONSHIPS BETWEEN TRANSMISSIBLE (TRANS-LOCATION, INVERSION) AND NON-TRANSMISSIBLE (DICENTRIC, RING) REARRANGEMENTS WILL BE EVALUATED ACCORDING TO THE DOSE AND DURATION OF THE CULTURE.
A COMPARISON OF THE EFFECT OF GAMMA-RAYS AND HEAVY IONS WILL ALSO BE UNDERTAKEN. IN PARTICULAR, RESEARCH INTO THE OCCURENCE OF CHROMOSOMAL LESIONS SPECIFIC TO CERTAIN KINDS OF RADIATION WILL BE CARRIED OUT.