Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint® Lectures Lectures by Greg Podgorski, Utah State University Are Viruses Alive? Current Issues in Biology, Volume 3 Scientific American

Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Concept Review Are Viruses Alive? Answering the question “Are viruses alive?” is difficult because a precise definition of what constitutes life is elusive. Viruses exist in a gray area between the living and nonliving. Viruses must replicate within a host cell.

Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Concept Review One way a virus replicates. Are Viruses Alive?

Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Concept Review Are Viruses Alive? Historically, research on viruses has focused on how they take over cells or cause disease, with little attention paid to their important role in evolution. Viruses are active agents of evolution and often exchange genetic information with their hosts. Viruses may add their genes to the genome of their hosts, possibly becoming a critical part of the host.

Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Concept Review Are Viruses Alive? The huge population of viruses, their intimate relationship with their host, and their rapid rates of replication and mutation make them a potent source of genetic innovation. Viruses now need to be studied within the web of life rather than viewing them exclusively as harmful infectious agents.

Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Testing Your Comprehension Are Viruses Alive? The genome of a virus may contain a) DNA. b) RNA. c) protein. d) DNA or RNA. e) DNA, RNA, or protein.

Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Testing Your Comprehension Are Viruses Alive? The genome of a virus may contain d) DNA or RNA.

Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Testing Your Comprehension Are Viruses Alive? Once a virus gains entry into a cell, its next step is to a) enter the nucleus. b) begin protein synthesis. c) begin synthesis of DNA or RNA, depending on the virus. d) release its genetic material.

Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Testing Your Comprehension Are Viruses Alive? Once a virus gains entry into a cell, its next step is to d) release its genetic material.

Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Testing Your Comprehension Are Viruses Alive? Viruses can play an active role in the evolution of their host species when they a) lose their pathogenic properties. b) transfer new genes to the host. c) acquire the ability to replicate independently of the host. d) become larger and more complex.

Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Testing Your Comprehension Are Viruses Alive? Viruses can play an active role in the evolution of their host species when they b) transfer new genes to the host.

Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Testing Your Comprehension Are Viruses Alive? A rapidly evolving virus a) does not mutate. b) has a low mutation rate. c) has a high mutation rate. d) has a low replication rate.

Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Testing Your Comprehension Are Viruses Alive? A rapidly evolving virus c) has a high mutation rate.

Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Biology and Society Strongly Agree Strongly Disagree A. E. C. B. D. Are Viruses Alive? Viruses have had little impact on human history.

Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Thinking About Science Are Viruses Alive? The genome of influenza virus is made of seven separate segments of RNA. Why would having multiple genome segments instead of one offer an advantage for producing new viral types? a) This increases the rate of mutation in each genome segment. b) If two or more viruses infect a cell simultaneously, the newly replicated viruses may contain a mixture of genome segments from the different infecting viruses. c) The rate of replication of a segmented genome is more rapid than for genomes made of one segment. d) A much larger number of viruses can be produced from infection with viruses with segmented genomes.

Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Thinking About Science Are Viruses Alive? The genome of influenza virus is made of seven separate segments of RNA. Why would having multiple genome segments instead of one offer an advantage for producing new viral types? b) If two or more viruses infect a cell simultaneously, the newly replicated viruses may contain a mixture of genome segments from the different infecting viruses.

Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Interpreting Data and Graphs Are Viruses Alive? Source: UNAIDS AIDS Epidemic Update 2004 If AIDS infection rates continue increasing at the rate they did between 2000–2004, then in 2012 there will be ______ people infected with the AIDS virus.

Copyright © 2006 Pearson Education, Inc. publishing as Benjamin Cummings Interpreting Data and Graphs Are Viruses Alive? Source: UNAIDS AIDS Epidemic Update 2004 If the current 2000–2004 rate of increase is maintained, there will be 52 million people infected with the AIDS virus.