What's happening: Shares of the gene-sequencing company Illumina (NASDAQ:ILMN) dropped by as much as 11% today on heavy volume following the release of its second-quarter results after the bell yesterday. For the quarter, Illumina posted $539 million in revenue, an increase of 21% compared to a year ago. The company also reaffirmed its annual revenue guidance for 2015, indicating that total revenue is expected to grow by approximately 20% for the full-year, even after accounting for a roughly 3% negative impact from foreign exchange rates. 

Why it's happening: The Street was expecting revenue to come in about $3 million higher for the three-month period at $542 million, marking the first time in nearly six years that Illumina has failed to meet consensus. This was also the third straight quarter the company saw its sales growth decline. Digging into Illumina's conference call, Illumina's President Francis deSouza said that sales of the company's high-end gene sequencer, known as HiSeq X, have fallen over the past year, which was the likely culprit behind this revenue miss. 

Is today's drop a buying opportunity? I think the answer is "yes", but with the caveat that investors will need to be patient to allow the top shelf section of the gene-sequencing market to mature. Big names like Roche have been pushing hard to find innovative new ways to employ this ground-breaking technology in the fight against cancer, but we're still not there yet. And until that happens, the demand for ultra-fast gene-sequencers is likely to remain relatively weak. 

George Budwell has no position in any stocks mentioned. The Motley Fool recommends Illumina. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.