in the x direction, the water wants to flow in that direction) For a given hydraulic. conductivity, the vertical flow rate depends on the sum of the gravitational potential energy. gradient per unit weight of water (dz/dz =1) and the vertical gradient in soil water pressure.
Origin and spread of the 1278insTATC mutation causing TayâSachs disease in Ashkenazi Jews: Genetic drift as a robust and parsimonious hypothesis. Human Genetics 114 (4): 366â376. pmid 14727180.
Tay-Sachs disease is caused by the absence or significantly reduced level of a vital enzyme called beta-hexosaminidase. It is the Hexosaminidase A (HEXA) gene in the DNA that provides instructions for making this enzyme. Without the correct amount of the HexA enzyme, a fatty substance or lipid called GM2 ganglioside accumulates abnormally in cells, especially in the nerve cells of the brain.