WASHINGTON — On Dec. 6, Chief Justice John G. Roberts Jr. asked a half-dozen probing questions during the argument of a patent case involving Life Technologies, which makes genetic testing kits. Later that week, if the court followed its usual practices, he met in private with his colleagues to discuss the case and cast his vote. If he was in the majority, as he is most of the time, he assigned the majority opinion to himself or to another justice.

On Wednesday, about a month after all of this, the Supreme Court announced that Chief Justice Roberts “has concluded that he should not continue to participate in this case.” He had discovered, the court said, that he owned 1,212 shares of the parent company of Life Technologies.

Corporate relationships can be tangled, but this one was relatively straightforward, and it was disclosed on the second page of the petition seeking review in the case. “Life Technologies Corporation is an indirect wholly owned subsidiary of Thermo Fisher Scientific Inc.,” the petition said. The statement was repeated on the second page of the company’s brief on the merits of the case.

Thermo Fisher Scientific was among the chief justice’s larger holdings. According to his latest financial disclosure report, released in June, his shares were worth between $100,001 and $250,000. At Friday’s closing price, the shares were worth about $178,000.