<prompt> True regarding galactosemiaMental retardation occursDefect in epimeraseDefect in galactose 1PO4 uridyl transferaseAll the above  <response>: Inability to metabolise galactose occurs in galactosemia which may be caused by deficiency of galactose-1-phosphate uridyl transferase,UDP-Galactose-4-Epirnerase and galactokinase.Out of three, most common is Galactose 1-phosphate uridyl transferase deficiency. 