Table 2.

Measurement of PCR Bias

Genotype (X:Y)	N*	MC(SMN1)X:Y	MN(SMN2)X:Y	SD† of N(SMN2)	MC(SMN2)X:Y	%SMN2X:Y	PBX:Y
2:0	13	1.902	0	0	0	0	N/A‡
1:1	27	1.018	1.028	0.088	0.724	6.6%	0.832
2:1	53	1.973	0.962	0.109	0.678	3.6%	0.788
3:1	11	2.938	0.948	0.107	0.668	2.9%	0.792
1:2	57	1.034	2.045	0.156	1.440	8.0%	0.801
2:2	81	2.033	2.001	0.184	1.409	6.5%	0.810
3:2	6	2.999	2.069	0.071	1.457	4.9%	0.843
1:3	16	1.063	3.181	0.199	2.241	10.0%	0.822
2:3	3	2.234	3.269	0.271	2.302	14.9%	0.923
1:4	4	1.097	4.057	0.184	2.857	13.3%	0.790

Each symbol is described in Table 1 . Note that PB_X:Y (SMN2 PCR efficiency relative to SMN1 PCR efficiency) is approximately 0.8, regardless of SMN genotype, except for the 2:3 (N = 3).

number of cases;

standard deviation;

not applicable.