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Chapter 16 Viruses Masks: ©Yuriy Dyachyshyn/AFP/Getty Images Copyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without.

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Presentation on theme: "Chapter 16 Viruses Masks: ©Yuriy Dyachyshyn/AFP/Getty Images Copyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without."— Presentation transcript:

1 Chapter 16 Viruses Masks: ©Yuriy Dyachyshyn/AFP/Getty Images Copyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.

2 Section 16.1 A virus is a small, infectious agent. It is genetic material wrapped in a protein coat. Viruses Are Genes Wrapped in a Protein Coat

3 Section 16.1 Viruses are very small. Figure 16.1

4 Viruses Are Genes Wrapped in a Protein Coat Section 16.1 Viruses come in many shapes and sizes. Figure 16.2

5 Viruses Are Genes Wrapped in a Protein Coat Section 16.1 Note the genetic material and the protein coat, or capsid. Figure 16.2

6 Viruses Are Genes Wrapped in a Protein Coat Section 16.1 The host range of a virus is the kind of organisms or cells that it can infect. The reservoir of a virus is the site where it exists in nature. Mosquito: USDA

7 Viruses Are Genes Wrapped in a Protein Coat Section 16.1 The host range of a virus is the kind of organisms or cells that it can infect. The reservoir of a virus is the site where it exists in nature. The virus that causes Yellow Fever has a host range that includes humans and has a reservoir in mosquitoes. Mosquito: USDA

8 Clicker Question #1 What organic molecules are found in all viruses? A. Carbohydrates and lipids B. Nucleic acids and carbohydrates C. Proteins and nucleic acids D. Lipids and proteins Flower: © Doug Sherman/Geofile/RF

9 Clicker Question #1 What organic molecules are found in all viruses? A. Carbohydrates and lipids B. Nucleic acids and carbohydrates C. Proteins and nucleic acids D. Lipids and proteins Flower: © Doug Sherman/Geofile/RF

10 16.1 Mastering Concepts What features do all viruses share? Masks: ©Yuriy Dyachyshyn/AFP/Getty Images

11 Viral Replication Occurs in Five Stages Section 16.2Figure 16.3 2 1 3 Protein coat Viral DNA Virus Receptor Transcription RNA Translation Coat proteins and other proteins Viral genes contain instructions for making viruses. Host cell Viral DNA Viral DNA Replication 3 4 5

12 Viral genes contain instructions for making viruses. Viral replication: 1. Virus attaches to host. 2 1 3 Protein coat Viral DNA Virus Receptor Transcription RNA Translation Coat proteins and other proteins Host cell Viral DNA Viral DNA Replication 3 4 5 Section 16.2Figure 16.3 Viral Replication Occurs in Five Stages

13 Viral genes contain instructions for making viruses. Viral replication: 1. Virus attaches to host. 2. Virus penetrates cell and releases its DNA. 2 1 3 Protein coat Viral DNA Virus Receptor Transcription RNA Translation Coat proteins and other proteins Host cell Viral DNA Viral DNA Replication 3 4 5 Section 16.2Figure 16.3 Viral Replication Occurs in Five Stages

14 Viral genes contain instructions for making viruses. Viral replication: 1. Virus attaches to host. 2. Virus penetrates cell and releases its DNA. 3. Host transcribes and translates viral DNA as if it were its own. 2 1 3 Protein coat Viral DNA Virus Receptor Transcription RNA Translation Coat proteins and other proteins Host cell Viral DNA Viral DNA Replication 3 4 5 Section 16.2Figure 16.3 Viral Replication Occurs in Five Stages

15 Viral genes contain instructions for making viruses. Viral replication: 1. Virus attaches to host. 2. Virus penetrates cell and releases its DNA. 3. Host transcribes and translates viral DNA as if it were its own. 4. New viruses assemble. 2 1 3 Protein coat Viral DNA Virus Receptor Transcription RNA Translation Coat proteins and other proteins Host cell Viral DNA Viral DNA Replication 3 4 5 Section 16.2Figure 16.3 Viral Replication Occurs in Five Stages

16 Viral genes contain instructions for making viruses. Viral replication: 1. Virus attaches to host. 2. Virus penetrates cell and releases its DNA. 3. Host transcribes and translates viral DNA as if it were its own. 4. New viruses assemble. 5. Viruses leave the cell. 2 1 3 Protein coat Viral DNA Virus Receptor Transcription RNA Translation Coat proteins and other proteins Host cell Viral DNA Viral DNA Replication 3 4 5 Section 16.2Figure 16.3 Viral Replication Occurs in Five Stages

17 Clicker Question #2 The five steps of viral replication are listed below in no particular order. If you were to arrange them in order, what step would come fourth? A. Assembly B. Penetration C. Release D. Attachment E. Synthesis Flower: © Doug Sherman/Geofile/RF

18 Clicker Question #2 The five steps of viral replication are listed below in no particular order. If you were to arrange them in order, what step would come fourth? A. Assembly B. Penetration C. Release D. Attachment E. Synthesis Flower: © Doug Sherman/Geofile/RF

19 16.2 Mastering Concepts What is the source of energy and raw materials for the synthesis of viruses in a host cell? Masks: ©Yuriy Dyachyshyn/AFP/Getty Images

20 Viruses Might or Might Not Kill Host Cells Section 16.3Figure 16.4 Viruses following the lytic pathway burst from their host cells.

21 Viruses Might or Might Not Kill Host Cells Section 16.3Figure 16.4 Viruses following the lysogenic pathway “hide” as they replicate.

22 Viruses Might or Might Not Kill Host Cells Section 16.3Figure 16.4 A prophage is the DNA of a lysogenic bacteriophage that is inserted into the host chromosome.

23 Viruses Might or Might Not Kill Host Cells Section 16.3Figure 16.4 The prophage replicates as the cell divides.

24 Viruses Might or Might Not Kill Host Cells Section 16.3Figure 16.4 At some point, viruses shift from a lysogenic infection to the lytic pathway.

25 Clicker Question #3 Viruses following the lytic pathway kill their host cell as they replicate. A. True B. False Flower: © Doug Sherman/Geofile/RF

26 Clicker Question #3 Viruses following the lytic pathway kill their host cell as they replicate. A. True B. False Flower: © Doug Sherman/Geofile/RF

27 16.3 Mastering Concepts What is the difference between a lytic and a lysogenic viral infection? Masks: ©Yuriy Dyachyshyn/AFP/Getty Images

28 Some Viruses Might Linger for Years Section 16.4Figure 16.5 HIV often remains latent; it does not immediately induce disease symptoms.

29 Some Viruses Might Linger for Years When HIV does replicate, it requires a few more steps than “typical” viral replication. Section 16.4Figure 16.5

30 Some Viruses Might Linger for Years HIV has an RNA genome. It must produce a DNA copy before incorporating genes into the host’s DNA. Section 16.4Figure 16.5

31 Drugs and Vaccines Help Fight Viral Infections Section 16.4 Vaccines “teach” your immune system to recognize a virus. Vaccination: ©Peter Cade/Iconica/Getty Images

32 Drugs and Vaccines Help Fight Viral Infections Vaccines “teach” your immune system to recognize a virus. Antiviral drugs are difficult to develop because of viruses high mutation rate. Section 16.4 Vaccination: ©Peter Cade/Iconica/Getty Images

33 Drugs and Vaccines Help Fight Viral Infections Vaccines “teach” your immune system to recognize a virus. Antiviral drugs are difficult to develop because of viruses high mutation rate. Antibiotics do NOT work against viruses. Section 16.4 Vaccination: ©Peter Cade/Iconica/Getty Images

34 Drugs and Vaccines Help Fight Viral Infections A vaccine has the molecular components of a virus but does not expose a person to the disease. Section 16.4Figure 16.6 Eggs: ©Stephen D. Cannerelli/The Image Works

35 Drugs and Vaccines Help Fight Viral Infections Scientists inject flu viruses into fertilized chicken eggs. The viruses replicate in the eggs. Section 16.4Figure 16.6 Eggs: ©Stephen D. Cannerelli/The Image Works

36 Drugs and Vaccines Help Fight Viral Infections Harvesting viruses from the eggs provides the raw materials to produce a vaccine. Section 16.4Figure 16.6 Eggs: ©Stephen D. Cannerelli/The Image Works

37 Clicker Question #4 Will taking left-over antibiotics help you fight off the flu? A. No, antibiotics will not work against flu viruses. B. Yes, but only if you have enough antibiotics left to kill all of the viruses. C. Yes, the antibiotics kill the bacteria that produce flu viruses. Flower: © Doug Sherman/Geofile/RF

38 Clicker Question #4 Will taking left-over antibiotics help you fight off the flu? A. No, antibiotics will not work against flu viruses. B. Yes, but only if you have enough antibiotics left to kill all of the viruses. C. Yes, the antibiotics kill the bacteria that produce flu viruses. Flower: © Doug Sherman/Geofile/RF

39 16.4 Mastering Concepts What is a latent virus? Masks: ©Yuriy Dyachyshyn/AFP/Getty Images

40 Viruses Also Cause Disease In Plants The color patterns on these plants might look interesting to us, but they’re caused by viruses. Section 16.5Figure 16.7 Leaf: ©Nigel Cattlin/Science Source; Tulip: ©Science VU/Visuals Unlimited

41 Viruses Also Cause Disease In Plants Viral infections often spread on the mouths of plant- eating insects. Section 16.5Figure 16.7 Leaf: ©Nigel Cattlin/Science Source; Tulip: ©Science VU/Visuals Unlimited

42 Viruses Also Cause Disease In Plants Although plants do not have an active immune system, they may prevent viral infections from spreading by degrading viral mRNA. Section 16.5Figure 16.7 Leaf: ©Nigel Cattlin/Science Source; Tulip: ©Science VU/Visuals Unlimited

43 16.5 Mastering Concepts How do viruses enter plant cells? Masks: ©Yuriy Dyachyshyn/AFP/Getty Images

44 Viroids and Prions Are Simpler Than Viruses Section 16.6Figure 16.8 Viroids are circles of RNA. Plants: USDA Plant Virology Laboratory/Theodore Diener

45 Viroids and Prions Are Simpler Than Viruses Viroids do not encode proteins, but they do use host cells to replicate. Section 16.6Figure 16.8 Plants: USDA Plant Virology Laboratory/Theodore Diener

46 Viroids and Prions Are Simpler Than Viruses The viroid shown here apparently interferes with the plant’s ability to make essential proteins. Section 16.6Figure 16.8 Plants: USDA Plant Virology Laboratory/Theodore Diener

47 Viroids and Prions Are Simpler Than Viruses A prion is a normal cellular protein that sometimes adopts an abnormal shape. Section 16.6Figure 16.9 Cow: ©Pixtal/age fotostock RF; Tissue: ©Ralph Eagle Jr./Science Source

48 Viroids and Prions Are Simpler Than Viruses Strangely, upon contact with an abnormally formed prion, a normal prion switches to the abnormal shape. Section 16.6Figure 16.9 Cow: ©Pixtal/age fotostock RF; Tissue: ©Ralph Eagle Jr./Science Source

49 Viroids and Prions Are Simpler Than Viruses Prions are responsible for mad cow disease. Section 16.6Figure 16.9 Cow: ©Pixtal/age fotostock RF; Tissue: ©Ralph Eagle Jr./Science Source

50 Clicker Question #5 Viroids and prions are infectious agents, but they are not types of viruses. A. True B. False Flower: © Doug Sherman/Geofile/RF

51 Clicker Question #5 Viroids and prions are infectious agents, but they are not types of viruses. A. True B. False Flower: © Doug Sherman/Geofile/RF

52 16.6 Mastering Concepts How are viroids and prions different from viruses? Masks: ©Yuriy Dyachyshyn/AFP/Getty Images

53 Investigating Life: Scientific Detectives Follow HIV’s Trail Section 16.7Figure 16.10 HIV likely originated as a related virus, called SIV, that is common in chimps.

54 Investigating Life: Scientific Detectives Follow HIV’s Trail Section 16.7Figure 16.10 Amino acid sequences of viral proteins helped researchers to build the evolutionary tree of these related viruses.

55 Investigating Life: Scientific Detectives Follow HIV’s Trail Section 16.7Figure 16.10 Humans who hunt chimps for meat were likely infected with SIV. The virus mutated in humans, giving rise to multiple strains of HIV.


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