Table 1. Statistical analysis of molecular combing data.

Signal	N	8-kb rDNA probe		N	11-kb rDNA probe
		Mean SD	95% C.I.		Mean SD	95% C.I.
A	185	11.1 19.0	–	61	11.8 9.5	–
B	206	3.5 0.6	0.04	77	5.3 1.0	0.22
C	192	3.4 0.6	0.04	57	2.4 0.7	0.18

One chromosome-XI probe labelled with Texas Red and two fluorescein-labelled rDNA probes of different sizes were used in FISH experiments. The 11-kb probe spanned both the rDNA unit and 3′ flanking region (Fig. 5A). All values are in µm (elongation factor: 2 kb/µm). The 95% confidence interval (95% C.I.) was calculated only for signals B and C, with normal size distributions. The difference between the mean signal C sizes for the two experiments is highly significant (Student’s t-test: t = 9.77, P < 0.001). N, number of measurements; SD, standard deviation.