The Swiss pharmaceutical giant Roche is nothing if not determined in its quest to acquire Illumina, the San Diego-based leader in genetic-sequencing equipment. In January, after Illumina’s board rebuffed Roche’s initial overtures, Roche made a $5.7 billion tender offer directly to shareholders. When that didn’t succeed, it extended the offer to midnight last Friday. Now Roche has upped its offer to $6.5 billion and is urging shareholders to vote for Roche’s independent director nominees at Illumina’s annual meeting to be held on April 18.