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Ch. 15 - DNA and the Gene: Synthesis and Repair
Freeman - Biological Science 7th Edition
Freeman7th EditionBiological ScienceISBN: 9783584863285Not the one you use?Change textbook
All textbooksFreeman 7th EditionCh. 15 - DNA and the Gene: Synthesis and RepairProblem 3
Chapter 15, Problem 3

How are Okazaki fragments synthesized?
a. By using the leading-strand template, and synthesizing 5'→3'
b. By using the leading-strand template, and synthesizing 3'→5'
c. By using the lagging-strand template, and synthesizing 5'→3'
d. By using the lagging-strand template, and synthesizing 3'→5'.

Verified step by step guidance
1
Understand that DNA replication involves the synthesis of new DNA strands using existing strands as templates. The two strands of DNA are antiparallel, meaning they run in opposite directions.
Recognize that DNA polymerase, the enzyme responsible for synthesizing new DNA, can only add nucleotides in the 5' to 3' direction. This is a key constraint in DNA replication.
Identify that the leading strand is synthesized continuously in the 5' to 3' direction as the replication fork opens. In contrast, the lagging strand is synthesized discontinuously.
Learn that Okazaki fragments are short sequences of DNA nucleotides synthesized discontinuously on the lagging strand. These fragments are later joined together by the enzyme DNA ligase.
Conclude that Okazaki fragments are synthesized using the lagging-strand template in the 5' to 3' direction, which corresponds to option c.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

DNA Replication

DNA replication is the process by which a cell duplicates its DNA, ensuring that each daughter cell receives an exact copy of the genetic material. It involves unwinding the double helix and synthesizing new strands using the original strands as templates. This process is crucial for cell division and is highly regulated to maintain genetic fidelity.
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Introduction to DNA Replication

Leading and Lagging Strands

During DNA replication, the two strands of the double helix are replicated differently due to their antiparallel nature. The leading strand is synthesized continuously in the 5' to 3' direction, while the lagging strand is synthesized discontinuously in short segments called Okazaki fragments, also in the 5' to 3' direction, due to the opposite orientation.
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Leading & Lagging DNA Strands

Okazaki Fragments

Okazaki fragments are short sequences of DNA nucleotides synthesized on the lagging strand during DNA replication. These fragments are created because DNA polymerase can only synthesize DNA in the 5' to 3' direction, necessitating a discontinuous approach on the lagging strand. They are later joined by DNA ligase to form a continuous strand.
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Related Practice
Textbook Question

Which of the following is not a property of DNA polymerase?

a. It adds dNTPs only in the 5'→3' direction.

b. It requires a primer to begin synthesis.

c. It opens the two strands of DNA at the replication fork.

d. Its exonuclease activity is involved in proofreading.

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Textbook Question

What is the function of primase?

a. Synthesis of the repetitive, short double-stranded DNA sequences required by DNA polymerase.

b. Synthesis of a short RNA strand that is complementary to single-stranded DNA.

c. Closing the gap at the 3′ end of DNA after excision repair.

d. Removing primers and synthesizing a short section of DNA to replace them.

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Textbook Question

Telomerase synthesizes DNA in the _____ direction.

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Textbook Question

Researchers design experiments so that only one thing is different between the treatments that are being compared. In the Hershey–Chase experiment, what was this single difference?

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Textbook Question

Analyze the following statements about DNA synthesis. Select True or False for each statement.

T/FAn RNA polymerase is essential for DNA synthesis.

T/FOkazaki fragments would be unnecessary if DNA polymerase could synthesize DNA in both the 3'→5' and 5'→3' directions.

T/FDNA ligase is used more frequently on the lagging strand than on the leading strand.

T/FToposiomerase is required to separate the two strands of DNA at the replication fork.

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