Master Race

The Master Race was the result of The Master stepping into the Immortality Gate on Earth. The gate sent out his genetic structure to every human on Earth to turn every one into a version of The Master. Only two humans escaped this fate, Donna Noble and Wilfred Mott.

The original Master was the leader of the race, although everyone else was exactly the same as him. No one seemed to disagree with this either and everyone was happy to do his bidding.

History
After transformation, The Master found out that Donna was still human as she called Wilfred. The Master then commanded everyone in the area of the call after having it tracked to bring her to him. They were all knocked out as Donna's defense mechanism, left in her mind by The Doctor, kicked in. After The Doctor escaped, The Master commanded all of the Masters who took over people of high military power to get ready all missiles and to search for The Doctor.

After the Immortality Gate was destroyed, The Master's genetic code was removed from the human race by Rassilon, bringing them back to normal and bringing the race back to only one person.