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.
If you appeared for jury service but were not chosen for a trial, you are exempt from serving for 18 months from the date of service. If you served on a jury panel for a trial or were part of a jury selection that took longer than two days, you are exempt from serving for two years from the last day of service.