Table 2.

The family-based case-control design: Transmitted alleles (cases) and nontransmitted alleles (controls) from 2N parents with one affected child

	Marker allele		Total
	M	M*
Cases
Observed number	a	b	a + b = 2N
Expected frequency			1/2
Controls
Observed number	c	d	c + d = 2N
Expected frequency	Q/2	(1 − Q)/2	1/2
Observed number	a + c	b + d	4N