In most multicellular organisms, every cell carries the same DNA, but this genetic information is used in varying ways by different types of cells. In other words, what a cell does within an organism dictates which of its genes are expressed.
Most enlisted positions require four years of active duty. If you join the Navy through an officer program, you must serve at least four of your eight years on active duty. However, pilots and flight officers must serve a minimum of eight to 10 years of active duty. Dentists, Medical Service Corps officers and nurses must serve a minimum of three years of active duty.
Complete Enlistment. When you join the Army, you agree to an enlistment. To fulfill the contract, you must serve for a set number of years. The Army enlistment options start at two years, and you can enlist for as many as six years. When you complete your enlistment, you receive your discharge.