US STOCKS-Wall Street flat with Yellen on tap; biotechs climb
* Dow Chemical to spin off unit, merge it with Olin
* Healthcare buoys indexes as biotechs bounce back
* Fed Chair Janet Yellen to speak shortly before the closing bell
* Indexes up: Dow 0.07 pct, S&P 0.11 pct, Nasdaq 0.28 pct (Updates to mid-afternoon)
By Chuck Mikolajczak
NEW YORK, March 27 (Reuters) - U.S. stocks were flat on Friday, with the S&P 500 on track for its worst week since late January, ahead of a speech by Federal Reserve Chair Janet Yellen that could create a volatile close on Wall Street.
Healthcare stocks helped buoy indexes with biotech stocks bounced 1.8 percent higher after suffering a 7-percent drop in the prior four sessions, while energy was the worst performing S&P sector as crude prices resumed their decline.
Fed Chair Yellen will speak on monetary policy in San Francisco just 15 minutes before the closing bell (1945 GMT) and traders will keep an ear out for clues on the timing of the start of the tightening path at the Fed.
"In the new chapter of 'no explicit forward guidance,' every speech does become incrementally more important," said Anastasia Amoroso, global market strategist with J.P. Morgan Funds in New York. Continuación...