ABSTRACT
Figure 21 Examples of some common fragile sites frequently seen in cultures which have been treated with methotrexate or other antagonists of folic acid metab olism. (a-e) Common fragile site at 3p l 4 stained by plain Giemsa (unhanded) and by Q banding showing (a) gap in both chromatids, (b) cell with single chromatid break, (c) cell with break in one chromatid and gap in the other, (d) cell with gap involving both chromatids in both homologs, and (e) cell with gap in chromatids of one homolog and chromatid break in the other homolog. Pairs of chromosome at right show common fragile sites (arrows) at lp3 1 .2 , 6q26, and 7q22.
