Shares of biotechnology companies opened mixed Friday as the broader market declined on troubles at government-backed mortgage companies Fannie Mae and Freddie Mac, and oil prices continued climbing.

Here's how several key biotechnology stocks performed Friday morning:

Gilead Sciences Inc., down 4 cents to $54.55.

Amgen Inc., up 4 cents to $51.73.

Biogen Idec Inc., up 53 cents to $61.47.

Genentech Inc., down 50 cents to $77.41.

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