Continental Airlines, which is operating under Chapter 11 of the U.S. Bankruptcy Code, estimates net income of $62.2 million for 1985, compared to $50.3 million in 1984 . . . GTE Mobilnet Inc., a unit of GTE Corp., said it acquired a majority interest in Cellular Communications of Irvine . . . Short interest on the New York Stock Exchange fell 35.3 million shares in the month ended Jan. 15 to a total of 266.6 million . . . Perkin-Elmer Corp. and Emeryville, Calif.-based Cetus Corp. have formed a partnership to develop instrument systems and related products for use in biotechnology research and development . . . Genentech declared a 2-for-1 stock split that will be payable to shareholders of record Feb. 1.