Sector Snap: Biotechnology

The major indexes plummeted in afternoon trading as reports showed that a majority in the House was voting against the package, which is the most sweeping government intervention in markets since the Great Depression.

Stocks were already trading lower on concerns the $700 billion aid package would fail, and as the votes rolled in, the Dow Jones industrial average plunged as much as 702 points. The Standard & Poor's 500 and Nasdaq composite index suffered comparable declines, although each index bounced back from their lows.

Meanwhile, the American Stock Exchange's biotechnology index, which tracks several bellwether companies, fell 18.54 points, or 2.3 percent, to 787.53 points. Drug developers, including large and established biotechnology companies, are normally considered defensive stocks, but the extreme volatility in the market is taking its toll.

Shares of Amgen Inc. fell $2.35, or 3.9 percent, to $58.32; while Genentech Inc. fell $4.71, or 5.2 percent, to $86.48. Elsewhere in the sector, Gilead Sciences Inc. fell $4.12, or 7.5 percent, to $45.21, Celgene Corp. fell $1.94, to 2.9 percent, and Cephalon Inc. fell $1.38 to $78.50.

Biogen Idec Inc. bucked the trend, rising 73 cents to $50.50.