VIRUSES

1 EJC H2 Biology T4W10 Viruses Genetics of Bacteria and Viruses - Viruses 1. Overview of Topic Viruses are biological entities which defy the definition of life. Outside of a host cell, a virus particle is nothing more than a speck of dust. However, once a virus infects a host cell, it has the capability of reproducing at the expense of the host itself. The Spanish flu which surfaced in 1918 lead to a pandemic which claimed more lives than those lost during the 1 st World War. Despite being one of the most microscopic entities in the biological world, viruses can threaten the existence of huma n life itself on earth. In this chapter, we will learn about the different types of viruses (Bacteriophages & Animal Viruses), their reproduction cycles as well as how they undergo evolution. 2. Learning Outcomes a. Discuss how viruses challenge the cell theory and concepts of what is considered living. b. Describe the structural components of viruses, including enveloped viruses and bacteriophages, and interpret drawings and photographs of them. c. Describe the structure and organisation of viral, prokaryotic and eukaryotic genomes (including DNA/RNA, single-/double-stranded, number of nucleotides, packing of DNA, linearity/circularity and presence/absence of introns). d. Describe how the genomes of viruses are inherited through outlining the reproductive cycles of: i. bacteriophages that reproduce via lytic cycle only, eg. T4 phage; ii. Bacteriophages that reproduce via lytic and lysogenic cycles, eg. Lambda phage; iii. enveloped viruses, eg. influenza iv. retroviruses, eg. HIV. e. Describe how variation in viral genomes arises, including antigenic shift and antigenic drift. 3. References  Biology, 9th Edition, by Campbell, N.A. and Reece J.B. (2011).  Microbiology – An Introduction, 9th Edition by Tortora, Funke and Case. (2007).  Molecular Biology of the Cell, 3rd Edition, by Alberts, Bray and Lewis. (2008).

2 EJC H2 Biology T4W10 Viruses Contents 1. Overview of Topic ...................................................................................................... 1 2. Learning Outcomes.................................................................................................... 1 3. References ................................................................................................................. 1 4. Introduction ............................................................................................................... 3 5. Viruses challenge the cell theory and the definition of an living organism .............. 4 6. Structure of Viruses ................................................................................................... 6 a. Genome ................................ ................................ ................................ ................. 6 b. Capsid ................................ ................................ ...................