"The Nemesis T-Type was an experimental form of Tyrant created by Umbrella Europe's Paris Lab. It's purpose was to prove that a t-virus-infected creature could be intelligent.
There were four Nemesis models developed by the European branch. One of them maintained the capability of independent thought during a stage of development, and attempted to escape, but was destroyed. The remaining three got their intelligence "restricted" and were fitted with inhibitor's to increase Umbrella's control over them. The Tyrant sent to Raccoon City during the outbreak was the second model, called Nemesis T-02. It was the only model that underwent a long period of training."
"As one of the rare individuals whose genetic make-up was capable of producing a Tyrant, Sergei became the genetic model for the majority of Umbrella's later Tyrant program, beyond the T-001 and T-002 projects initiated by the team led by Albert Wesker and William Birkin. Sergei also ordered the re-engineering of two T-103 Tyrants in order to produce his personal bodyguards, known as "Ivan". The 10 clones of Sergei would later form the basis of the T-103 model, which shaped every Umbrella manufactured Tyrant model thereafter. The mass production of T-103's which was spearheaded on Sheena Island was based on the initial Sergei clones, whilst T-103's implanted with the NE-α Parasite became Nemesis T-Type."
Source:Resident Evil Wiki
I think this makes it clear...