The Question is from neet-botany , and it was created by the author D VINOD

Question

When DNA replication starts

D VINOD · Accepted Answer

## CORE INFORMATION
✓ **Answer**: [B]
## CONCEPT FRAMEWORK
	**Primary Concept**: DNA Replication Initiation
	**Related Topics**: DNA Structure, Hydrogen Bonding, Enzyme Action (Helicase)
	**Prerequisites**: Basic understanding of DNA structure (double helix, base pairing), and the process of DNA replication.
## SOLUTION PATHWAY
**Given Information**:
	The question asks what happens at the *start* of DNA replication.
	The correct answer must be related to the initial steps of the process.
**Method & Steps**:
	1. **Understand the process**: DNA replication starts with unwinding of the double helix.
		Reasoning: The two strands of DNA need to be separated to serve as templates for new strands.
		Formula/Rule: None directly applicable at this step.
	2. **Identify the bonds**: The double helix is held together by hydrogen bonds between complementary base pairs.
		Working: Hydrogen bonds are relatively weak and can be broken by enzymes.
		Key Point: Phosphodiester bonds within each strand are stronger and not broken during strand separation.
	3. **Relate bonds to replication start**: The unwinding process requires the breaking of hydrogen bonds.
		Result: Therefore, the correct answer is that hydrogen bonds between the nucleotides break.
		Verification: This action allows the two DNA strands to separate for replication.
 ## OPTION ANALYSIS
[A] :x: Okazaki fragments are produced on the lagging strand *after* the initial unwinding. This is not a step in the initiation of DNA replication.
[B] ✓: This is correct. The hydrogen bonds between the bases are what holds the double helix together, and they must be broken to separate the strands.
[C] :x: Phosphodiester bonds are the backbone of the DNA strand; they are not broken during replication, only during DNA damage or repair.
[D] :x: The bonds between the base and deoxyribose are also part of the backbone and not broken during the unwinding phase of replication.
 ## LEARNING AIDS
	**Common Mistakes**:
		1. Confusing phosphodiester bonds with hydrogen bonds: Remember that phosphodiester bonds are within the DNA backbone, while hydrogen bonds are between the strands.
		2. Misunderstanding the timing of Okazaki fragment formation: These fragments are formed during lagging strand synthesis, not at the very start of replication.
	**Quick Tips**:
		1. Visualize the DNA double helix: Imagine the two strands held together by weak hydrogen bonds that are easily separated.
		2. Remember the role of helicase: This enzyme breaks hydrogen bonds to unwind DNA.

D VINOD · Answer

The leading strand produces Okazaki fragments

D VINOD · Answer

The correct Option is "The hydrogen bonds between the nucleotides of two strands break"

D VINOD · Answer

The phosphodiester bonds between the adjacent nucleotides break

D VINOD · Answer

The bonds between the nitrogen base and deoxyribose sugar break

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