Complex Correlation of Brain Hemispheric Laterality with Hand-use Preference

through generations, and it does not directly concern itself with cellular differentiation required for development in higher multicellular organisms. Indeed, in the 1940s, developmental biologists, believing that genes were not important for development, went their separate ways from geneticists. How could the multiple arrays of cell types be generated when all cells of an organism possess the same set of genes questioning the importance of genetics to development? They thought something other than genes must be important for development. Only after the discovery of the phenomenon of gene regulation in Escherichia coli (Jacob and Monod 1961) did these fields begin to converge. Questions still remain unanswered about how development occurs. What controls the expressions of genes that regulate development with such remarkable precision such that different organs develop only at specific locations on the body? Thus far, the major paradigm for developmental gene regulation comprises the “morphogen-gradient model” (Brown and Wolpert 1990) that remains to be experimentally verified. For example, it is not known what controls the development of human brain laterality whereby left and right hemispheres structurally and functionally differ from one another. Because there is an unexplained partial association of human leftversus right-hand-use preference with the hemisphere of the brain that develops language, handedness and brain laterality development must be somehow related. Furthermore, an excess of left-handedness is associated with psychiatric diseases of schizophrenia and bipolar disorders; anomalies of brain laterality development may be relevant for disease causation. In this broad overview, we will discuss possible connections between the seemingly unrelated fields of cell-type determination in fission yeast and brain development in humans. We will summarize results of studies that suggest that the traits of brain laterality, handedness, and psychosis development result from an embryonic asymmetric cell division. A mitotic cell genetic (“mitogenetics”) model postulates that a Watson versus Crick DNA strand-specific imprinting of a chromosome and its patterned segregation produces differentiated daughter cells and that psychosis results from genetics, without a conventional Mendelian gene mutation in families carrying chromosome 11 rearrangements. COMPLEX CORRELATION OF BRAIN HEMISPHERIC LATERALITY WITH HAND-USE PREFERENCE