Mean Percentage of Mitotic Nuclei Per Brain in Each Class.

For each genotype, the percentage of nuclei containing chromosomal breaks and tetraploidy was calculated for 6 individual brains and mean percentages determined. 23–132 mitotic nuclei per individual brain were analyzed. Four classes of abnormal karyotypes (see Figure 2): I) Normal karyotype with no breaks. II) Diploid nuclei containing breaks. II + IV) All nuclei containing breaks. III) Tetraploid nuclei without breaks. III + IV) Total tetraploid nuclei including those with breaks. IV) Tetraploid nuclei with breaks.