Why is it important for a single gene to be able to produce hundreds or thousands of the same RNA molecules?

It is important because the genes are the blue prints to keep the master plan, RNA, safe.

Explanation:

a symbiotic relationship with the mitochondria

blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart. as the ventricle contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs where it is oxygenated.