Professor R. Szymanski has injected an accelerator and DNA into your brain to make you more intelligent. Just as the DNA was at the required level there was an explosion in the lab which sent the Professor into a coma. He was the only one who knew how to stop the experiment so a navy assault ship is shrunk and injected into your blood stream to go and stop the DNA from growing. Eight pieces of a growth inhibitor must be collected before facing your brain. With a foreign body in your blood, blood cells and other parts of your body are trying to destroy you. You must battle these to hopefully get to the brain and stop your brain from exploding. Another hindrance is the fact that you have to find all the inter-cellular junctions to move about the body. Some require keys. Plasma spheres can be found along the way to upgrade your ship and weapons. DNA warrior is a horizontally side-scrolling shoot-em-up. The joystick will steer your ship while the fire button will fire your weapon. Pressing the space bar will select your next upgrade when a plasma sphere is collected. Also seen on the screen is a energy gauge, score and a ship upgrade to select.