Does a mutated X-linked dominant transcriptional repressor gene explain mirror writing ability and synaesthesia?

SummaryX-linked dominant conditions tend to present as two distinct sex-dependent phenotypes. Mirror writing ability and synaesthesia both appear to fall into this category. The existence of two different phenotypes in these two conditions is advanced as a reason associated with regarding their genetic mode of transmission as being X-linked dominant. The alternative autosomal mode cannot account for different male and female phenotypes.It is suggested that the gene for mirror writing ability, a trait linked to non-right-handedness, negates the normal process of left-lateralisation of language. Similarities between mirror writing ability and synaesthesia are documented and it is further suggested that these similarities can be explained if the genes for each condition are regarded as target genes for the same mutated X-linked dominant transcriptional repressor gene, possibly MeCP2.