Abstract
Sister chromatid exchanges are studied in 17 normal animals and one carrier of 1/29 centric fusion. A mean of 12.2 exchanges per cell is found on the total animals studied. An analysis of variance done on 11 normal subjects to compare their mean number of exchanges per cell shows a significant individual difference at the 0.5% threshold. Homologous chromosome exchanges are very rare with the exception of one animal which had 4 on 8 cells studied and a quadriradial formation. The fused chromosome presents a variable number of exchanges comparable to those of free homologues.
