During the kiwi DNA isolation procedure, what is the purpose of placing the mixture in an ice bath after heating?

• A. It decreases chemical reaction rate
• B. It speeds up reaction rate
• C. It denatures proteins
• D. It dissolves DNA

Answer: (C)

In DNA isolation from kiwi, controlling proteins that could interfere with the DNA is the key idea. Heating helps break open cells and denature many proteins, releasing the DNA. Placing the mixture in an ice bath quickly lowers the temperature and keeps those proteins in an unfolded, non‑functional state, effectively inactivating enzymes that might otherwise degrade the DNA. So the ice bath’s role is to denature proteins and prevent them from acting on the DNA, which is why this step is described as denaturing proteins. It’s not about speeding up reactions or dissolving DNA; it’s about turning off the proteins that could interfere with DNA recovery.