Handedness, language dominance and aphasia: a genetic model.
A simple two-allele Mendelian model of the genetics of handedness is described and fitted to data in the literature. The model proposes that there are two alleles, D (dextral) and C (chance), the homozygous DD genotype producing only right-handers (directional asymmetry), the homozygous CC genotype producing a racemic mixture of 50% right-handers and 50% left-handers (fluctuating asymmetry), and the heterozygote, DC, being intermediate between the homozygotes and producing 25% left-handers, and 75% right-handers. It is also suggested that the true population incidence of left-handedness is 7.75%, deviations from this figure being due to either criterion shifts or selection biases. The same model is then fitted, by means of a number of minor conceptual extensions, to data from the literature on the relationship of handedness to language dominance, acute and permanent aphasia, and visual processing dominance.
D001037:Aphasia / Q000235:genetics*; D001925:Brain Damage, Chronic / Q000503:physiopathology; D002540:Cerebral Cortex / Q000503:physiopathology; D004007:Dichotic Listening Tests; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006225:Hand / Q000502:physiology; D006801:Humans; D007802:Language; D008297:Male; D008957:Models, Genetic; D010641:Phenotype; D013060:Speech / Q000502:physiology; D014427:Twins; D014796:Visual Perception / Q000502:physiology