For this to happen the DNA must replicate itself exactly. When DNA replicates itself and the cell divides both of the new cells that are produced contain the exact same DNA (barring mutations) which means both new cells can code to make the same proteins.
Americium was first produced in 1944 by the group of Glenn T. Seaborg at the University of California, Berkeley. Although it is the third element in the transuranic series, it was discovered fourth, after the heavier curium.
Following the lighter neptunium, plutonium, and heavier curium, americium was the fourth transuranium element to be discovered. At the time, the periodic table had been restructured by Seaborg to its present layout, containing the actinide row below the lanthanide one.