The Securities and Exchange Commission yesterday approved a propasal to allow the trading of options on Government National Mortgage Association securities, a move expected to generate a new source of money for the construction industry.

In approving the proposal of the Chicago Board Options Exchange, the commission moved into the new area, allowing securities exchanges it regulates to expand from trading equity-options (such as stock options) into new products such as the GNMA options.

It also marks the first time that an SEC-regulated securities exchange will be dealing in the same market as a commodity exchange.

What the SEC did is allow the CBOE to create a standardized market for GNMA securities. GNMA is a part of the Department of Housing and Urban Development. It issues securties called Ginnie Maes that represent shares in pools of mortgages insured by the Federal Housing Administration and the Veterans Administration.

SEC officials said yesterday they expect the market will be used by mortgage bankers and others to hedge commitments they have made.

THE CBOE anticipates that trading will begin in the new market in October.

Commission members took some pains, however, to indicate that approving GNMA options trading did not mean an automatic nod for other types of nonequity options such as options on foreign currency.