TABLE 2

Expected maternal and offspring genotypic values for four scenarios that mimic various patterns of genomic imprinting

Offspring genotype
LLSLLSSSEmbedded Image
a.
Maternal genotype
    LL22222
    LS, SL00000
    SS−2−2−2−2−2
Embedded Image11−1−1
b.
Maternal genotype
    LL02241
    LS,SL−20020
    SS−4−2−20−1
Embedded Image−11−11
c.
Maternal genotype
    LL12231.5
    LS,SL−10010
    SS−3−2−2−1−1.5
Embedded Image01−10
d.
Maternal genotype
    LL13332
    LS,SL−11110.5
    SS−3−1−1−1−2
Embedded Image0200
  • In all cases the locus has no true imprinting effect (i.e., io = 0). Table format is identical to Table 1. (a) Maternal-effect locus mimicking maternal expression. The pattern is caused by an additive maternal effect (am = 2) with p = q = 0.5. (b) Maternal-effect locus mimicking paternal expression. Here, an additive maternal effect (am = 2) shows the same magnitude of negative pleiotropic effect as the direct additive effect (ao = −2). (c) Maternal-effect locus mimicking bipolar dominance imprinting that is caused by an additive maternal effect (am = 2) and a weaker negative pleiotropic additive direct effect (ao = −1). (d) Maternal-effect locus mimicking polar overdominance. Here, the maternal effect (am = 2) shows a weaker negative pleiotropic than additive effect (ao = −1). In addition, there is a dominance direct effect (do = 1). In all cases, the allele frequency is set to p = q = 0.5. It should be noted that in all cases the allele frequency does not affect the pattern of genotypic values (although it does affect the actual values themselves). Boldface values correspond to maternal–offspring genotype combinations that cannot exist under Mendelian inheritance.