is the type 1 error rate for the genetic association study.
Maternal genetic effect is the proportion of variance in the trait explained by maternal genetic effects at the locus.
Offspring genetic effect is the proportion of variance in the trait explained by offspring genetic effects at the locus.
If you have an effect size estimate and allele frequency for the genetic variant of interest, you can calculate the proportion of variance in the trait explained as
(2*P*(1-P)*b^2)/VAR(trait), where P=allele frequency, b=effect size estimate.
NB. Maternal and offspring genetic effects can only be estimated uniquely when there are genotyped individuals who report their own phenotype and genotyped individuals who report their offspring's phenotype. These individuals do not need to be overlapping.
If you use the Maternal and Offspring Effects Power Calculator in your research please cite: Moen G, Hemani G, Warrington NM, Evans DM (accepted). Calculating power to detect maternal and offspring genetic effects in genetic association studies. Behav Genet.