Table 3.

Measured ratio and number of chromosomes

Experiment	G 19/22	WS 212	T 21 a	T 21 b	T 21 c
Chr 21	21.04	61.95	34.05	35.75	117.78
Chr 9	20.63	68.83	21.97	21.93	71.82
Chr 21/Chr 9	1.02	0.90	1.55	1.63	1.64

Cosmids were hybridized and detected as described. Hybridization fragments were recorded and measured, and the respective sums of each set of signal lengths were used to calculate the corresponding number of chromosomes. The ratio is the number of (target) chromosome 21 (Chr 21) equivalents to the number of (control) chromosome 9 (Chr 9) equivalents.