Presentation is loading. Please wait.

Presentation is loading. Please wait.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 19.1 0.5 mm Viruses: A Borrowed Life.

Similar presentations


Presentation on theme: "Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 19.1 0.5 mm Viruses: A Borrowed Life."— Presentation transcript:

1 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 19.1 0.5 mm Viruses: A Borrowed Life

2 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Discovery of Viruses: Scientific Inquiry 1935, Wendell Stanley crystallized tobacco mosaic virus (TMV) © 2011 Pearson Education, Inc.

3 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 19.2 Extracted sap from tobacco plant with tobacco mosaic disease RESULTS Passed sap through a porcelain filter known to trap bacteria Healthy plants became infected Rubbed filtered sap on healthy tobacco plants 1234

4 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 19.2b

5 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 19.2c

6 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Structure of Viruses Not cells Consists of nucleic acid enclosed in a protein coat and, in some cases, a membranous envelope © 2011 Pearson Education, Inc.

7 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Viral Genomes – Double- or single-stranded DNA, or – Double- or single-stranded RNA © 2011 Pearson Education, Inc.

8 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 19.3 Capsomere of capsid RNA Capsomere DNA Glycoprotein Glycoproteins Membranous envelope RNA Capsid Head DNA Tail sheath Tail fiber 18 250 nm 80 225 nm 70–90 nm (diameter) 80–200 nm (diameter) 20 nm 50 nm (a) Tobacco mosaic virus (b) Adenoviruses (c) Influenza viruses(d) Bacteriophage T4

9 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Some viruses have viral envelopes Derived from the host cells membrane © 2011 Pearson Education, Inc.

10 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Bacteriophages (phage) viruses that infect bacteria © 2011 Pearson Education, Inc.

11 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Lytic Cycle Attachment 1

12 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 19.5-2 Attachment 21 Entry of phage DNA and degradation of host DNA

13 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 19.5-3 Attachment 213 Entry of phage DNA and degradation of host DNA Synthesis of viral genomes and proteins

14 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 19.5-4 Attachment 2143 Entry of phage DNA and degradation of host DNA Synthesis of viral genomes and proteins Assembly Phage assembly Head TailTail fibers

15 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 19.5-5 Attachment 21543 Entry of phage DNA and degradation of host DNA Release Synthesis of viral genomes and proteins Assembly Phage assembly Head TailTail fibers

16 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Lysogenic Cycle Replicates the phage genome without destroying the host © 2011 Pearson Education, Inc. Animation: Phage Lambda Lysogenic and Lytic Cycles

17 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 19.6 New phage DNA and proteins are synthesized and assembled into phages. The cell lyses, releasing phages. Phage Phage DNA The phage injects its DNA. Bacterial chromosome Lytic cycle lytic cycle is induced or Phage DNA circularizes. Certain factors determine whether lysogenic cycle is entered Lysogenic cycle Prophage Daughter cell with prophage Occasionally, a prophage exits the bacterial chromosome, initiating a lytic cycle. Cell divisions produce a population of bacteria infected with the prophage. The bacterium reproduces, copying the prophage and transmitting it to daughter cells. Phage DNA integrates into the bacterial chromosome, becoming a prophage.

18 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings New phage DNA and proteins are synthesized and assembled into phages. The cell lyses, releasing phages. Phage Phage DNA The phage injects its DNA. Bacterial chromosome Lytic cycle lytic cycle is induced or Phage DNA circularizes. Certain factors determine whether lysogenic cycle is entered Figure 19.6a

19 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings lytic cycle is induced or Phage DNA circularizes. Certain factors determine whether lysogenic cycle is entered Lysogenic cycle Prophage Daughter cell with prophage Occasionally, a prophage exits the bacterial chromosome, initiating a lytic cycle. Cell divisions produce a population of bacteria infected with the prophage. The bacterium reproduces, copying the prophage and transmitting it to daughter cells. Phage DNA integrates into the bacterial chromosome, becoming a prophage. Figure 19.6b

20 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Table 19.1a

21 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Table 19.1b

22 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings RNA as Viral Genetic Material Retroviruses use reverse transcriptase to copy their RNA genome into DNA HIV (human immunodeficiency virus) is the retrovirus that causes AIDS (acquired immunodeficiency syndrome) © 2011 Pearson Education, Inc.

23 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Glycoprotein Reverse transcriptase HIV Viral envelope Capsid RNA (two identical strands) HOST CELL Viral RNA Reverse transcriptase RNA-DNA hybrid DNA NUCLEUS Provirus Chromosomal DNA RNA genome for the next viral generation mRNA New virus Figure 19.8a

24 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 19.8c HIV Membrane of white blood cell HIV entering a cell

25 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 19.8d HIV entering a cell 0.25 m

26 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 19.8e New HIV leaving a cell

27 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 19.8f New HIV leaving a cell

28 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 19.8g New HIV leaving a cell

29 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Evolution of Viruses Probably evolved as bits of cellular nucleic acid e.g. Plasmids, transposons, and viruses are all mobile genetic elements © 2011 Pearson Education, Inc.

30 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Viral Diseases in Animals Viruses may damage or kill cells by causing the release of hydrolytic enzymes from lysosomes Some viruses cause infected cells to produce toxins that lead to disease symptoms Others have molecular components such as envelope proteins that are toxic © 2011 Pearson Education, Inc.

31 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Vaccines are harmless derivatives of pathogenic microbes that stimulate the immune system to mount defenses against the harmful pathogen © 2011 Pearson Education, Inc.

32 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Emerging Viruses e.g. influenza virus H1N1 Flu epidemics © 2011 Pearson Education, Inc.

33 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Viral diseases in a small isolated population can emerge and become global Viral strains that jump species can exchange genetic information with other viruses to which humans have no immunity © 2011 Pearson Education, Inc.

34 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Can cause pandemics, global epidemics The 2009 flu pandemic was likely passed to humans from pigs; for this reason it was originally called the swine flu © 2011 Pearson Education, Inc.

35 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 19.9a 2009 pandemic H1N1 influenza A virus (a) 1 m

36 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 19.9b (b) 2009 pandemic screening

37 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 19.9c (c) 1918 flu pandemic

38 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Viral Diseases in Plants Most plant viruses have an RNA genome © 2011 Pearson Education, Inc.

39 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 19.10a

40 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 19.10c

41 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Viroids and Prions: The Simplest Infectious Agents Viroids are small circular RNA molecules that infect plants and disrupt their growth Prions are slow-acting, virtually indestructible infectious proteins that cause brain diseases in mammals Convert normal proteins into the prion version e.g. mad cow disease, and Creutzfeldt-Jakob disease in humans are all caused by prions © 2011 Pearson Education, Inc.

42 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 19.11 Prion Normal protein Original prion New prion Aggregates of prions


Download ppt "Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 19.1 0.5 mm Viruses: A Borrowed Life."

Similar presentations


Ads by Google