Nineteen probands with benign epilepsy of childhood and centrotemporal EEG foci (rolandic discharges), 36 of their full parents, and 34 full siblings were included in a genetic study. In these sibships (excluding probands), 15% (5/34) had seizures and rolandic discharges, and 19% (6/32) had rolandic discharges alone. Of the full parents, 11% (5/38) had seizures in chilhood but none in adult life. Only 1 parent (3%) of 36 had rolandic discharges. There was no differnence with sex. The results were tested against different genetic hypotheses and indicate that an autosomal dominant gene with age-dependent penetrance is responsible for the EEG trait.

In a population the optimal phenotype is promoted by buffering mechanisms that keep inter- and intra-individual variation low. A link exists between canalization, that controls phenotypic variation, and developmental stability, mostly measured as fluctuating asymmetry of bilateral traits (FA). Both types of variation are associated with the functional importance of a trait, and both are increased by stress of various kinds. But there are also several instances of non-congruence. The concept of developmental stability has been found elusive, and low FA is not the unambiguous measure of well being and good genes that has been claimed. It can be concluded that developmental stability is partly governed by specific, as yet unknown, molecular processes.

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Genetic identity, which may be important for kin recognition, is the fraction of the genome that is identical by descent. It is, except for the parent-offspring relation, governed by probability and its variance depends on the number of segregating units during meiosis. Using the recombination index as an approximation of this number the variance for genetic identity has been estimated for different kinds of kinship.