In the 50 years since the structure of DNA was elucidated, giant strides have been made in understanding what genes are and how they work. Currently, scientists are able to use this information to diagnose patients with hereditary disease, and alter plant and micro-organism genes to manufacture foodstuffs and medicines.
In the future we may be able to cure diseases such as TB, cancer and heart disease that have killed millions of people over the years. We may also be able to alter our own DNA or grow new organs for ourselves. It remains to be seen whether this is entirely safe or desirable.