Final answer:
Specific proteins can be removed from cellular extract in in vitro replication systems by targeted denaturation or precipitation using antibodies or ammonium sulfate.
Step-by-step explanation:
In in vitro replication systems using cellular extracts, specific proteins can be removed from the preparation for the purpose of analyzing how their absence affects the replication process through targeted denaturation by altered pH or temperature, and precipitation of the protein with specific antibodies or ammonium sulfate to remove it from solution.