A publicly held genetic analysis company based in Santa Clara will pay $330 million in cash to acquire San Diego biotech firm eBioscience Inc., the companies said Nov. 30.

Affymetrix Inc., which sells its technologies to pharmaceutical, diagnostic and biotechnology companies, said the acquisition will round out its product offerings and allow it to make headway into the lucrative oncology and immunology markets.

The company said it would not be making changes to eBioscience’s management team and will keep the operations in San Diego.

EBioscience, located in Torrey Pines, has 280 employees and is expected to top $70 million in revenues this year, said Doug Farrell, vice president of investor relations for Affymetrix. “It’s an exceptionally well run company that’s growing fast,” Farrell said. “We have no plans to change the company’s structure or location, just allow them to continue to do what they’ve been doing.”

Founded in 1999, privately held eBioscience specializes in flow cytometry, a technique for analyzing many different types of particles simultaneously within a single cell or a population of cells. The approach is useful for learning about disease on a cellular level, Farrell said. eBioscience has thousands of products that it sells to research institutes and cancer centers, with a smaller segment of business in clinical diagnostics, he said.

“EBioscience complements our traditional businesses of genomics and cytogenetics, and dramatically strengthens our foundation in molecular diagnostics,” said Stephen P.A. Fodor, founder and chairman of Affymetrix.

Affymetrix, with 2010 revenues of $310 million, trades on Nasdaq under the symbol AFFX.

— Kelly Quigley