Final answer:
Actinomycin D is beneficial at low doses because it inhibits DNA and RNA synthesis, which can help prevent the growth and replication of cancer cells.
Step-by-step explanation:
At low concentrations, actinomycin D, also known as dactinomycin, inhibits DNA directed RNA synthesis. This means that it prevents the formation of RNA molecules from DNA templates. At higher concentrations, actinomycin D also inhibits DNA synthesis. This can be beneficial because it can help prevent the growth and replication of cancer cells, which require DNA and RNA synthesis for their survival. Actinomycin D is commonly used in chemotherapy to treat various types of cancer.