Usage of "Which"

“Which”の使い方について

◎ Which: Which is used to introduce non-restrictive information or it is used to provide additional information about something.

Example: Recombinant genomes, which express chloramphenicol acetyltransferase in mammalian cells, are infectious in 293 cells.

In this example, the which clause merely gives additional information about recombinant genomes; which clauses are usually set off by commas.