Difficulty: Hard

Average Score: 48%

Which of the following steps in DNA replication would occur second?

Rationale

DNA molecule separates into two template strands.

During DNA replication, the second step involves the separation of the DNA double helix into two single strands, which serves as templates for synthesizing new complementary strands. This unwinding is essential for allowing the addition of nucleotides during the subsequent steps of replication.

A (Complimentary nucleotides are added to each template strand.) YOUR ANSWER

This choice refers to the step where new nucleotides are incorporated into the growing strands of DNA. However, this occurs after the DNA strands have already separated and the template strands are accessible, making it the third step in the replication process, not the second.

B (DNA molecule separates into two template strands.) CORRECT

This is the correct answer as it represents the second step in the DNA replication process where the hydrogen bonds between the base pairs are broken, allowing the two strands of DNA to separate and serve as templates for the new strands.

C (Two DNA molecules, each with a template strand and a new strand, are formed.) YOUR ANSWER

This choice describes the final outcome of DNA replication rather than a step in the process. The formation of two separate DNA molecules occurs after the addition of new nucleotides, which follows the separation of the original strands.

D (DNA molecule unwinds.) YOUR ANSWER

While unwinding is a crucial initial step in DNA replication, it occurs before the separation of the strands. Therefore, it is the first step, not the second, in the overall replication process.

Conclusion

In DNA replication, the correct sequence of events is crucial for understanding how genetic material is copied. The second step is the separation of the DNA molecule into two template strands, allowing complementary nucleotides to be added subsequently. Each of the other choices represents either a precursor to this step or a consequence of the replication process, highlighting the importance of order in molecular biology.

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