Shares of Illumina Inc. have fallen nearly 10 percent this week after the gene-sequencing company announced second-quarter revenue missed analysts’ expectations on Tuesday.

Sales for the quarter were $539 million, San Diego-based Illumina said in a statement Tuesday, falling short of the $542 million average of analysts’ estimates compiled by Bloomberg. The company hadn’t fallen short of analysts’ sales expectations since the third quarter of 2009.

Illumina makes gene-sequencing machines used by hospitals, researchers and pharmaceutical companies. Results of the tests are used to help develop new treatments as well as to analyze tumors that can be targeted by drugs.

Shares are trading on the Nasdaq under the stock symbol ILMN for $214.45 per share.