Table 2.

Parent of origin and meiotic outcome of nondisjunction error of chromosome 21 with mean parental age at conception of Down syndrome child in the rural and urban families

Parent of origin	Meiotic outcome group	DS sample from poor rural population				DS sample from urban and semi-urban population as reported in Ghosh et al. (2010)
		Sample size	Percent	Maternal age in year (mean ± SD)	Paternal age in year (mean ± SD)	Sample size	Percent	Maternal age in year (mean ± SD)	Paternal age in year (mean ± SD)
Maternal	MIa	135	59.21	24.92 ± 7.1	32.91 ± 4.25	131	77.51	27.62 ± 5.61	33.82 ± 6.77
	MIIb	93	40.78	26.63 ± 4.2	34.22 ± 3.1	38	22.49	29.02 ± 2.32	34.04 ± 5.21
	Stage unknown	10				8
	Subtotal	238	88.15			177	88.06
Paternal	MI	10	43.46	25.02 ± 3.4	31.07 ± 4.6	8	47.06	24.57 ± 3.11	30.26 ± 4.12
	MII	13	56.52	28.44 ± 6.12	35.02 ± 28	9	52.94	27.01 ± 5.03	34.33 ± 4.14
	Stage unknown	3				3
	Subtotal	26	9.63			20	9.95
Mitotic		6	2.23			4	1.99
Origin unknown		9				11

^aMeiosis I nondisjunction

^bMeiosis II nondisjunction