Table of contents

1. Introduction to Biology2h 42m
2. Chemistry3h 37m
3. Water1h 26m
4. Biomolecules2h 23m
5. Cell Components2h 26m
6. The Membrane2h 31m
7. Energy and Metabolism2h 0m
8. Respiration2h 40m
9. Photosynthesis2h 49m
10. Cell Signaling59m
11. Cell Division2h 47m
12. Meiosis2h 0m
13. Mendelian Genetics4h 44m
14. DNA Synthesis2h 27m
15. Gene Expression3h 6m
16. Regulation of Expression3h 31m
17. Viruses37m
- Viruses
  37m
18. Biotechnology2h 58m
19. Genomics17m
- Genomes
  17m
20. Development1h 5m
21. Evolution3h 1m
22. Evolution of Populations3h 53m
23. Speciation1h 37m
24. History of Life on Earth2h 6m
25. Phylogeny2h 31m
26. Prokaryotes4h 59m
27. Protists1h 12m
28. Plants1h 22m
29. Fungi36m
- Fungi
  19m
- Fungi Reproduction
  17m
30. Overview of Animals34m
- Overview of Animals
  34m
31. Invertebrates1h 2m
32. Vertebrates50m
33. Plant Anatomy1h 3m
34. Vascular Plant Transport1h 2m
- Water Potential
  1h 2m
35. Soil37m
- Soil and Nutrients
  20m
- Nitrogen Fixation
  16m
36. Plant Reproduction47m
- Flowers
  33m
- Seeds
  14m
37. Plant Sensation and Response1h 9m
38. Animal Form and Function1h 19m
39. Digestive System1h 10m
- Digestion
  1h 3m
- Blood Sugar Homeostasis
  7m
40. Circulatory System1h 49m
41. Immune System1h 12m
42. Osmoregulation and Excretion50m
- Osmoregulation and Excretion
  50m
43. Endocrine System1h 4m
- Endocrine System
  1h 4m
44. Animal Reproduction1h 2m
- Animal Reproduction
  1h 2m
45. Nervous System1h 55m
- Neurons and Action Potentials
  1h 8m
- Central and Peripheral Nervous System
  46m
46. Sensory Systems46m
- Sensory System
  46m
47. Muscle Systems23m
- Musculoskeletal System
  23m
48. Ecology3h 11m
49. Animal Behavior28m
- Animal Behavior
  28m
50. Population Ecology3h 41m
51. Community Ecology2h 46m
52. Ecosystems2h 36m
53. Conservation Biology24m
- Conservation Biology
  24m

14. DNA Synthesis

Introduction to DNA Replication

General Biology

14. DNA Synthesis

Introduction to DNA Replication

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1:06 minutes

Problem 6

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.

Verified step by step guidance

Understand the role of RNA polymerase: RNA polymerase is primarily involved in the synthesis of RNA from a DNA template during transcription, not DNA synthesis. DNA synthesis requires DNA polymerase, not RNA polymerase.

Consider the directionality of DNA synthesis: DNA polymerase synthesizes DNA only in the 5' to 3' direction. Okazaki fragments are short sequences synthesized on the lagging strand because DNA polymerase cannot synthesize in the 3' to 5' direction. If DNA polymerase could synthesize in both directions, Okazaki fragments would not be necessary.

Examine the function of DNA ligase: DNA ligase is an enzyme that joins DNA fragments together. On the lagging strand, multiple Okazaki fragments are synthesized, requiring DNA ligase to join them. The leading strand is synthesized continuously, so DNA ligase is used less frequently.

Clarify the role of topoisomerase: Topoisomerase helps relieve the tension in the DNA helix during replication but does not separate the strands. Helicase is the enzyme responsible for unwinding and separating the two strands at the replication fork.

Review each statement based on the explanations provided: Use the understanding of each enzyme's role and the process of DNA synthesis to determine the truthfulness of each statement.

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Key Concepts

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

DNA Polymerase Directionality

DNA polymerase synthesizes DNA in the 5' to 3' direction, which is crucial for understanding why Okazaki fragments are formed. On the lagging strand, DNA polymerase must work in short segments, creating Okazaki fragments, because it cannot synthesize in the 3' to 5' direction. This limitation necessitates the discontinuous synthesis of DNA on the lagging strand.

Role of DNA Ligase

DNA ligase is an enzyme that joins DNA fragments together by forming phosphodiester bonds. It is used more frequently on the lagging strand during DNA replication because it is responsible for connecting the Okazaki fragments into a continuous strand. On the leading strand, DNA synthesis is continuous, requiring less frequent use of DNA ligase.

Function of Topoisomerase

Topoisomerase is an enzyme that helps relieve the tension in the DNA helix ahead of the replication fork by cutting, unwinding, and rejoining DNA strands. It is not directly involved in separating the two strands of DNA; this task is performed by helicase. Topoisomerase ensures that the DNA does not become overly coiled or tangled during replication.

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