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

DNA Repair

General Biology

14. DNA Synthesis

DNA Repair

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1:35 minutes

Problem 10b

Textbook Question

The graph that follows shows the survival of four different E. coli strains after exposure to increasing doses of ultraviolet light. The wild-type strain is normal, but the other strains have a mutation in either a gene called uvrA, a gene called recA, or both.

(b) What are the relative contributions of these genes to the repair of UV damage?

Verified step by step guidance

Observe the graph which shows the survival rate of four E. coli strains after exposure to increasing doses of UV light. The strains include wild-type, uvrA mutant, recA mutant, and uvrA and recA double mutant.

Note that the wild-type strain maintains a high survival rate across all doses of UV light, indicating effective repair mechanisms for UV-induced damage.

The uvrA mutant shows a significant decrease in survival as the UV dose increases, suggesting that the uvrA gene plays a crucial role in repairing UV damage.

The recA mutant also shows a decrease in survival, but it is less severe than the uvrA mutant, indicating that recA contributes to repair but is not as critical as uvrA.

The double mutant (uvrA and recA) has the lowest survival rate, demonstrating that both genes are important for UV damage repair, with uvrA having a more pronounced effect than recA.

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Key Concepts

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

DNA Repair Mechanisms

DNA repair mechanisms are essential cellular processes that correct damage to the DNA molecule. In bacteria like E. coli, these mechanisms include nucleotide excision repair and recombinational repair, which help maintain genomic integrity after exposure to damaging agents such as ultraviolet (UV) light. Understanding these mechanisms is crucial for analyzing how different strains of E. coli respond to UV-induced damage.

uvrA Gene

The uvrA gene encodes a protein that is part of the nucleotide excision repair pathway, which recognizes and removes bulky DNA lesions caused by UV light. Mutations in the uvrA gene can impair the cell's ability to repair UV-induced damage, leading to increased cell death when exposed to UV radiation. This gene's role is critical in understanding the survival rates of different E. coli strains under UV exposure.

recA Gene

The recA gene is vital for homologous recombination and DNA repair in bacteria. It facilitates the repair of DNA double-strand breaks and is involved in the SOS response, which is activated in response to extensive DNA damage. Mutations in the recA gene can significantly affect a cell's ability to survive UV damage, making it important to analyze its contribution alongside the uvrA gene in the context of the experiment.

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Related Practice

Textbook Question

What aspect of DNA structure makes it possible for the proteins of nucleotide excision repair to recognize many different types of DNA damage?

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Textbook Question

What aspect of DNA structure makes it possible for the proteins of nucleotide excision repair to recognize many different types of DNA damage?

(b) the antiparallel orientation of strands in the double helix

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Textbook Question

What aspect of DNA structure makes it possible for the proteins of nucleotide excision repair to recognize many different types of DNA damage?

(a) the polarity of each DNA strand

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Textbook Question

The spontaneous loss of amino groups from adenine in DNA results in hypoxanthine, an uncommon base, opposite thymine. What combination of proteins could repair such damage?

a. Nuclease, DNA polymerase, DNA ligase

b. Telomerase, primase, DNA polymerase

c. Telomerase, helicase, single-strand binding protein

d. DNA ligase, replication fork proteins, adenylyl cyclase

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Textbook Question

The graph that follows shows the survival of four different E. coli strains after exposure to increasing doses of ultraviolet light. The wild-type strain is normal, but the other strains have a mutation in either a gene called uvrA, a gene called recA, or both.

(a) Which strains are most sensitive to UV light? Which strains are least sensitive?

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Multiple Choice

Researchers found a strain of E. coli bacteria that had mutation rates one hundred times higher than normal. Which of the following statements correctly describes the most likely cause of these mutations?

Which of the following statements is/are correct with regard to individuals with the disorder xeroderma pigmentosum?

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Multiple Choice

Which set of enzymes is involved in nucleotide excision repair?

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