A MODEL FOR SPECIFICATION OF THE LEFT-RIGHT AXIS IN VERTEBRATES

The mechanisms that underlie the formation of the left-right embryonic axis in vertebrates are not known, The programmed pattern of cell-typ e change in fission yeast results from the inheritance of specific chr omatids of the parental chromosome. Here, I address how such a model m ay explain left-right specification of the viscera in mice. The model proposes that DNA replication produces different chromatids, and that these specific chromatins of both homologs are nonrandomly segregated to daughter cells to specify the left-right axis of the embryo. Such a model presents a simple explanation of the interesting phenotype of t he newly discovered insertional mutation inv in mice, which causes rev ersal of the left-right axis, proposing that it is caused by a chromos omal inversion.