Answer: Exaggerate
Step-by-step explanation:
When something is overstated it is assumed to be more than it actually is which means that it is exaggerated. For instance, the General overstated the enemy numbers in order to gain public sympathy. This means that the General exaggerated enemy numbers and said they were more than they actually were.
The sentence in the question therefore means that understanding DNA structure cannot be exaggerated in terms of importance.