. 2019 Aug 30;22(2):301–308. doi: 10.1038/s41436-019-0636-5

Table 3.

Allele frequency in the mixture of maternal and fetal cell-free DNA

MM-FF	Prob	f_A
AA-AA	$p (p + q F_{1}) (p + q F_{2})$	$1 - e_{A B}$
AB-AB	$p q (1 - F_{1}) (1 - F_{2})$	$1 ∕ 2 + 1 ∕ 2 (e_{B A} - e_{A B})$
BB-BB	$q (q + p F_{1}) (q + p F_{2})$	e_BA
AA-AB	$p q (p + q F_{1}) (1 - F_{2})$	$(1 - h ∕ 2) (1 - e_{A B}) + h ∕ 2 e_{B A}$
BB-AB	$p q (q + p F_{1}) (1 - F_{2})$	$h ∕ 2 + e_{A B} - h ∕ 2 (e_{A B} + e_{B A})$
AB-AA	$p q (1 - F_{1}) (p + q F_{2})$	$(1 ∕ 2 + h ∕ 2) (1 - e_{B A}) + (1 ∕ 2 - h ∕ 2) e_{A B}$
AB-BB	$p q (1 - F_{1}) (q + p F_{2})$	$(1 ∕ 2 - h ∕ 2) (1 - e_{B A}) + (1 ∕ 2 + h ∕ 2) e_{A B}$

Fetal fraction (FF) is denoted by h. The column marked “Prob” is the probability of the joint genotypes in the first column. f_A denotes frequency of A allele conditioning on joint genotypes, taking into account sequencing error.