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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0:44 minutes

Problem 7

Textbook Question

A biochemist isolates, purifies, and combines in a test tube a variety of molecules needed for DNA replication. When she adds some DNA to the mixture, replication occurs, but each DNA molecule consists of a normal strand paired with numerous segments of DNA a few hundred nucleotides long. What has she probably left out of the mixture?
a. DNA polymerase
b. DNA ligase
c. Okazaki fragments
d. Primase

Verified step by step guidance

Understand the process of DNA replication, which involves the synthesis of a new DNA strand complementary to the template strand. This process requires several enzymes and components.

Recognize that during DNA replication, the leading strand is synthesized continuously, while the lagging strand is synthesized in short segments known as Okazaki fragments.

Identify the role of DNA ligase in DNA replication. DNA ligase is responsible for joining the Okazaki fragments on the lagging strand, creating a continuous DNA strand.

Consider the problem description: the DNA molecules consist of a normal strand paired with numerous segments of DNA a few hundred nucleotides long. This suggests that the Okazaki fragments are not being joined together.

Conclude that the absence of DNA ligase in the mixture is likely the reason for the presence of unjoined Okazaki fragments, as DNA ligase is needed to connect these fragments into a continuous 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, ensuring that each daughter cell receives an exact copy of the genetic material. It involves unwinding the double helix, synthesizing new strands using existing strands as templates, and requires various enzymes and proteins to facilitate the process.

Okazaki Fragments

Okazaki fragments are short sequences of DNA nucleotides synthesized discontinuously on the lagging strand during DNA replication. These fragments are later joined together by DNA ligase to form a continuous strand, as DNA polymerase can only synthesize DNA in the 5' to 3' direction.

DNA Ligase

DNA ligase is an enzyme crucial for DNA replication and repair, responsible for joining Okazaki fragments on the lagging strand. It catalyzes the formation of phosphodiester bonds between adjacent DNA fragments, ensuring the continuity and integrity of the newly synthesized DNA strand.