OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

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Which best describes the process of DNA replication?

The DNA strands merge into one
The DNA 'unzips' and new strands form through base pairing
The cell divides, creating two cells
DNA is converted to RNA

The correct answer is: The DNA 'unzips' and new strands form through base pairing

The process of DNA replication involves the unwinding of the double helix structure of DNA, often described as the DNA 'unzipping.' This occurs when the hydrogen bonds between the nucleotide base pairs are broken, separating the two strands of the DNA molecule. Once the strands are separated, enzymes like DNA polymerase facilitate the formation of new complementary strands by pairing free nucleotides with the exposed bases of the original strands. This process ensures that each new DNA molecule contains one original strand and one newly synthesized strand, which is crucial for genetic fidelity during cell division. In contrast, other options do not represent the correct process of DNA replication. The merging of DNA strands does not occur during replication; instead, two separate strands are formed. While cell division is a necessary step after DNA replication, it is not a description of the replication process itself. Additionally, the conversion of DNA to RNA refers to transcription, a different process altogether that occurs when cells need to synthesize proteins. The focus of this question is specifically on the replication of DNA, making the second option the most accurate description.