Final answer:
The enzyme required to unwind the DNA during replication is helicase, which separates the DNA strands by breaking hydrogen bonds, allowing access for DNA polymerase to synthesize new strands.
Step-by-step explanation:
The enzyme needed to unwind the DNA double helix during DNA replication is known as helicase. Helicase separates the two strands of DNA at the origin of replication by breaking the hydrogen bonds between the nucleotides. This unwinding allows other enzymes, such as DNA polymerase, to access the single-stranded DNA to synthesize a new complementary strand.
If helicase is mutated, the strands would not separate at the beginning of replication, thereby impeding the entire replication process.