The MiG 1.44 was a prototype stealth aircraft developed in the 1990s meant to compete with the F-22 and the Eurofighter, in that it was built with stealth capabilities for the air superiority role, but also with a large air-to-ground payload. The MiG 1.44 was also said to have a top speed of over 1,500 MPH at altitude, and a wing span of about 49 feet. The MiG 1.44 also looks similar to the J-20 as the photo below shows.
If Russia did provide China with help in building the J-20, it would not be the first time that the Russians/Soviets gave the Chinese help in producing military equipment. Back in the 1950s the Soviets gave the Chinese help in producing Chinese versions of the MiG-15 fighter (J-2), AK-47 assault rifle (Type 56), and the T-55 Main Battle Tank (Type 59). After the Sino-Soviet split during the 1960s, China aligned with the U.S. (this affects America's foreign policy and domestic policy to this day), but in recent years has mended relations with Russia and is now much friendlier than during the Cold War.
There is some speculation by the folks over DoDBuzz that Russia might be intentionally givng China help with the J-20 to increase the number of stealth fighters vs the number of F-22s and F-35s. Aviation Week also quotes a Russian analyst who speculates that China might have paid Russia for the tail of the MiG 1.44 and some parts.
If the Russians did provide the Chinese assistance with the J-20, it is not only a dangerous precedent, but at the same time it shows that Russia is willing to sell anything to anybody with a big enough wallet.
Photo Credit: Wikipedia, Global Security