 chang dna rna protein synthesi develop len len cell dna rna protein synthesi develop mous ey studi tritium-label thymidin uridin l- leucin autoradiograph techniqu mous embryon len epitheli cell undergo dna synthesi entir anterior len surfac birth ey open percentag epitheli cell undergo dna synthesi rapidli decreas percentag epitheli cell undergo dna synthesi constant germin zone local len equat region rna synthesi occur nucleat cell develop len embryon stage eyelid open len matur uridin incorpor rna superfici cell pattern tritium incorpor l-leucin 