Patterns of exchange induced by mitomycin C in C-bands of human chromosomes. I. Relationship to C-band size in chromosomes 1, 9, and 16.
Frequencies of exchange were determined in C-bands of chromosomes 1, 9 and 16 in six normal males, and related to relative C-band area. Comparing these different chromosomes, more exchanges occurred on average in 9 than in 1 although their mean C-band sizes were similar. Chromosome 16 exchanges were fewer, both overall and relative to C-band area. Comparing the same chromosome between individuals, there was a positive correlation between relative frequency and band size in both 1-1 and 9-9 exchanges. No clear trend was observed for other exchange events. If homology is required for interchange, it cannot be dependent solely on overall C-band size. Perhaps certain DNA sequences, sensitive to mitomycin C damage, are located in part of each C-band, with less per unit area in chromosome 1 than in 9 and still less in chromosome 16. X- and U-type exchanges between chromosome 9s occurred in near equal frequencies in all individuals. If synapsis of specific, affected sequences is a pre-requisite for interchange, this observation suggests that the affected sequence in chromosome 9 is arranged in both orientations relative to the centromere.
D002871:Chromosome Banding; D002900:Chromosomes, Human, 1-3 / Q000648:ultrastructure*; D002902:Chromosomes, Human, 16-18 / Q000648:ultrastructure*; D002906:Chromosomes, Human, 6-12 and X / Q000648:ultrastructure*; D003434:Crossing Over, Genetic / Q000187:drug effects*; D006801:Humans; D008297:Male; D016685:Mitomycin; D008937:Mitomycins / Q000494:pharmacology*
D008937:Mitomycins; D016685:Mitomycin