Table of contents

1. Introduction to Genetics51m
2. Mendel's Laws of Inheritance3h 37m
3. Extensions to Mendelian Inheritance2h 41m
4. Genetic Mapping and Linkage2h 28m
5. Genetics of Bacteria and Viruses1h 21m
6. Chromosomal Variation1h 48m
7. DNA and Chromosome Structure56m
8. DNA Replication1h 10m
9. Mitosis and Meiosis1h 34m
10. Transcription1h 0m
11. Translation58m
12. Gene Regulation in Prokaryotes1h 19m
13. Gene Regulation in Eukaryotes44m
14. Genetic Control of Development44m
15. Genomes and Genomics1h 50m
16. Transposable Elements47m
17. Mutation, Repair, and Recombination1h 6m
18. Molecular Genetic Tools19m
- Genetic Cloning
  9m
- Methods for Analyzing DNA
  9m
19. Cancer Genetics29m
- Overview of Cancer
  21m
- Cancer Mutations
  7m
20. Quantitative Genetics1h 26m
21. Population Genetics50m
- Hardy Weinberg
  19m
- Allelic Frequency Changes
  31m
22. Evolutionary Genetics29m

8. DNA Replication

Overview of DNA Replication

Genetics

8. DNA Replication

Overview of DNA Replication

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2:04 minutes

Problem 1d

Textbook Question

In the discussion, we focused on how DNA is replicated and synthesized. We also discussed recombination at the DNA level. Along the way, we encountered many opportunities to consider how this information was acquired. On the basis of these discussions, what answers would you propose to the following fundamental questions?
How do we know that DNA synthesis is discontinuous on one of the two template strands?

Verified step by step guidance

Understand the concept of DNA replication: DNA replication is semi-conservative, meaning each new DNA molecule consists of one original strand and one newly synthesized strand. The process involves the unwinding of the double helix and the synthesis of complementary strands.

Learn about the directionality of DNA synthesis: DNA polymerase synthesizes DNA in the 5' to 3' direction. This creates a challenge because the two strands of DNA are antiparallel, meaning one strand runs 5' to 3' while the other runs 3' to 5'.

Explore the concept of leading and lagging strands: The strand that is synthesized continuously in the 5' to 3' direction is called the leading strand. The other strand, which runs in the opposite direction, is synthesized discontinuously in short fragments called Okazaki fragments. This strand is known as the lagging strand.

Examine experimental evidence: The discovery of Okazaki fragments provided direct evidence for discontinuous synthesis. Researchers observed small DNA fragments during replication, which were later joined together by DNA ligase to form a continuous strand.

Understand the role of enzymes: DNA primase lays down RNA primers on the lagging strand to initiate synthesis of each Okazaki fragment. DNA polymerase extends these fragments, and DNA ligase seals the gaps between them. This enzymatic activity confirms the discontinuous nature of synthesis on the lagging strand.

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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 before cell division. It involves unwinding the double helix and synthesizing new strands complementary to each template strand. This process is crucial for genetic continuity and occurs in a semi-conservative manner, meaning each new DNA molecule consists of one old and one new strand.

Leading and Lagging Strands

During DNA replication, the two strands of the double helix are replicated differently. The leading strand is synthesized continuously in the direction of the replication fork, while the lagging strand is synthesized discontinuously in short segments called Okazaki fragments, which are later joined together. This difference is due to the antiparallel nature of DNA strands and the directionality of DNA polymerase.

Okazaki Fragments

Okazaki fragments are short sequences of DNA synthesized on the lagging strand during DNA replication. They are formed because DNA polymerase can only add nucleotides in a 5' to 3' direction, necessitating the synthesis of these fragments in the opposite direction of the replication fork. Understanding Okazaki fragments is essential for grasping why DNA synthesis is discontinuous on the lagging strand.

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Multiple Choice

What would happen to DNA replication in DNA polymerase lost its 3' to 5' exonuclease activity?

Which of the following proteins is responsible for synthesizing RNA primers?

The short DNA fragments created during lagging strand replication are called what?

In the discussion, we focused on how DNA is replicated and synthesized. We also discussed recombination at the DNA level. Along the way, we encountered many opportunities to consider how this information was acquired. On the basis of these discussions, what answers would you propose to the following fundamental questions?

What observations reveal that a 'telomere problem' exists during eukaryotic DNA replication, and how did we learn of the solution to this problem?

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Textbook Question

How do we know that in vivo DNA synthesis occurs in the 5' to 3' direction?

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Textbook Question

How was it demonstrated that DNA synthesis occurs under the direction of DNA polymerase III and not polymerase I?

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Textbook Question

Write a short essay that distinguishes between the terms replication and synthesis, as applied to DNA. Which of the two is most closely allied with the field of biochemistry?

478

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Textbook Question

Compare conservative, semiconservative, and dispersive modes of DNA replication.

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