* JPMorgan slides; Wells Fargo gains after results
* Nasdaq falls through 4,000 for first time since Feb. 5
* Dow off 0.8 pct; S&P 500 down 0.8 pct; Nasdaq off 1.3 pct (Updates to late afternoon)
By Angela Moon
NEW YORK, April 11 Selling accelerated in U.S. stocks on Friday as a lousy week came to a close, with biotech and tech shares again leading the Nasdaq lower and JPMorgan's disappointing earnings giving investors a reason to sell some bank stocks.
Biotech and momentum stocks extended losses from the previous session's sharp selloff that pushed the Nasdaq to its worst decline since Nov. 9, 2011. The Nasdaq Composite fell through 4,000 for the first time since early February and many of these popular shares are now down substantially from records reached only six or seven weeks ago.
Equities have been volatile this week, with Thursday's slide a sharp reversal from Wednesday's gains after minutes from the latest Federal Reserve policymakers' meeting suggested members were more likely to keep rates low than previously expected.
Since reaching a record intraday high on April 4, the S&P 500 has fallen 4.2 percent, while the Nasdaq has dropped 8.5 percent from its March 6 intraday high.
The Dow Jones industrial average fell 121.38 points or 0.75 percent, to 16,048.84. The S&P 500 lost 14.78 points or 0.81 percent, to 1,818.30. The Nasdaq Composite dropped 50.894 points or 1.26 percent, to 4,003.212.
JPMorgan Chase & Co shares fell 3.3 percent to $55.49 as the biggest drag on the S&P 500 after it reported a far weaker-than-expected quarterly profit as revenue from securities trading fell.
The S&P financial index lost 0.9 percent and was the S&P 500's worst-performing sector.
The Nasdaq biotech index fell 2.5 percent after rising as much as 1 percent earlier. The Global X social media index, which includes Facebook and LinkedIn , slid 2.4 percent.
In contrast to the day's sharp downturn, shares of Wells Fargo & Co rose 1.8 percent to $48.59 after the biggest mortgage lender in the United States reported a 14 percent increase in first-quarter net profit.
Even with the recent declines, investors appear committed to equities. Investors in U.S.-based funds poured $8.9 billion into stock funds in the week ended April 9, data from Thomson Reuters' Lipper service showed on Thursday. (Reporting by Angela Moon; Editing by Nick Zieminski and Jan Paschal)