The objective of this research is to analyze normal and abnormal mechanisms of development through use of mutant genes of the mouse. The particular mutation to be studied is ichthyosis (ic), a recessive mutation that causes abnormal clumping of nuclear chromatin in leucocytes, in addition to the abnormality of skin and hair. The effect of the mutation on macromolecular synthesis in cultured lymphocytes will be investigated, and an attempt will be made to detect qualitative and quantitative effects of the gene on nuclear histones and acidic proteins.