If a recombinant protein is toxic what effect can it have on the host?

Correct answer: Growth may slow or cell death may occur

A recombinant protein is made by a host cell after a foreign gene has been introduced and expressed. If that protein is toxic, its production can damage cell structures or interfere with essential cellular processes. The host may grow more slowly, produce less protein, show poor survival, or die when expression is too strong. The exact effect depends on the protein, its amount, and the host, so the word “may” is important.

Option A is correct because toxic expression can cause slow growth or cell death. A toxic protein will not make the host grow faster, turn into water, or automatically remove a marker. Researchers often use an inducible or otherwise controlled expression system so that production begins only under selected conditions and at a manageable level. This helps the host grow before expression and reduces harmful effects.