Scientists should control most possible variables in experiments to get the most valid and correct data. If many variables are included in experiments it is more difficult to interpret what is causing a different outcome.
Sulfur is a group six element in period 3 with atomic number 16 and an electronic configuration of 2:8:6. Therefore, to attain a stable configuration it requires to gain two electrons forming an ion with a charge of -2. The negative charge is due to the gaining of electrons.
The DNA is identical because all of your cells came from that one cell through mitosis which gives and exact copy of the DNA. All body cells got the complete "instruction manual" for the body, but only uses the proteins needed.
