Both the Sukhoi-27 and MiG-29 were designed by
TsAGI. They made the design and handed it to the Sukhoi and MiG bureaux. Sukhoi built a larger plane, and MiG built a smaller plane.
There is nothing in PRC that could have preceded either the Sukhoi-27 or the MiG-29 programmes, because, these programmes commenced
after TsAGI was done with its design phase.