..................... are enzymes that unwind DNA helices while .................. break and reseal the strands.

Explanation

To answer the question, we need to identify the enzymes involved in the processes of unwinding DNA helices and breaking and resealing the strands.

### Step-by-Step Solution:

1. **Identify the first enzyme**: The question asks for the enzyme that unwinds DNA helices. The enzyme responsible for this function is known as **helicase**. Helicase unwinds the DNA double helix by breaking the hydrogen bonds between the complementary base pairs.

2. **Identify the second enzyme**: The second part of the question refers to the enzyme that breaks and reseals the DNA strands. This function is performed by **topoisomerases**. Topoisomerases help relieve the tension that builds up ahead of the replication fork by making cuts in the DNA strands, allowing them to unwind, and then resealing them.

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