Multiple Choice
In DNA replication, an old DNA strand is used as a _____ for the assembly of a new DNA strand.
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8. DNA Replication
Overview of DNA Replication
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Based on the following replication bubble, which of these statements is true?
A
DNA synthesis occurs in the 5' to 3' direction on both the leading and lagging strands.
B
DNA polymerase can initiate synthesis of a new strand without a primer.
C
Both parental DNA strands serve as templates for the synthesis of the lagging strand only.
D
The leading strand is synthesized discontinuously in short fragments.
Verified step by step guidance1
Understand the directionality of DNA synthesis: DNA polymerase synthesizes new DNA strands in the 5' to 3' direction, meaning nucleotides are added to the 3' end of the growing strand.
Recognize the structure of the replication bubble: It has two replication forks where DNA unwinds, and each parental strand serves as a template for new strand synthesis.
Identify the leading strand: It is synthesized continuously in the 5' to 3' direction toward the replication fork because its template runs 3' to 5'.
Identify the lagging strand: It is synthesized discontinuously in short fragments called Okazaki fragments, also in the 5' to 3' direction but away from the replication fork, requiring multiple primers.
Evaluate the given statements based on these principles: DNA synthesis always occurs 5' to 3' on both strands, DNA polymerase requires a primer to initiate synthesis, both parental strands serve as templates for leading and lagging strands, and the leading strand is synthesized continuously, not discontinuously.
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