This document discusses viruses and virology. It defines viruses and describes their characteristics, including that viruses are acellular and can only replicate inside host cells. The document outlines viral replication methods and how viruses were first discovered. It also covers virus classification based on genetic material and morphology. Examples are provided of different virus types that infect humans, plants, and bacteria. The impact of viruses on disease and their relationship to cancer is summarized.

1. James M. Mitchell, MD

2. Pray Always
Luke 21:34-36 New King James Version (NKJV)
The Importance of Watching
34 “But take heed to yourselves, lest your hearts be weighed down with carousing,
drunkenness, and cares of this life, and that Day come on you unexpectedly. 35 For it will
come as a snare on all those who dwell on the face of the whole earth. 36 Watch therefore,
and pray always that you may be counted worthy to escape all these things that will come to
pass, and to stand before the Son of Man.”

3. Pray Always
Mark 14:32-42 New King James Version (NKJV)
The Prayer in the Garden
32 Then they came to a place which was named Gethsemane; and He said to His disciples,
“Sit here while I pray.” 33 And He took Peter, James, and John with Him, and He began to be
troubled and deeply distressed. 34 Then He said to them, “My soul is exceedingly sorrowful,
even to death. Stay here and watch.”
35 He went a little farther, and fell on the ground, and prayed that if it were possible, the hour
might pass from Him. 36 And He said, “Abba, Father, all things are possible for You. Take this
cup away from Me; nevertheless, not what I will, but what You will.”
37 Then He came and found them sleeping, and said to Peter, “Simon, are you sleeping?
Could you not watch one hour? 38 Watch and pray, lest you enter into temptation. The spirit
indeed is willing, but the flesh is weak.”
39 Again He went away and prayed, and spoke the same words. 40 And when He returned, He
found them asleep again, for their eyes were heavy; and they did not know what to answer
Him.
41 Then He came the third time and said to them, “Are you still sleeping and resting? It is
enough! The hour has come; behold, the Son of Man is being betrayed into the hands of
sinners. 42 Rise, let us be going. See, My betrayer is at hand.”

4. Pray Always
Mark 13:32-37 New King James Version (NKJV)
No One Knows the Day or Hour
32 “But of that day and hour no one knows, not even the angels in heaven, nor the Son, but only the
Father. 33 Take heed, watch and pray; for you do not know when the time is. 34 It is like a man going
to a far country, who left his house and gave authority to his servants, and to each his work, and
commanded the doorkeeper to watch. 35 Watch therefore, for you do not know when the master of
the house is coming—in the evening, at midnight, at the crowing of the rooster, or in the
morning— 36 lest, coming suddenly, he find you sleeping. 37 And what I say to you, I say to all:
Watch!”

5. Pray Always
John 18:4-9 New King James Version (NKJV)
4 Jesus therefore, knowing all things that would come upon Him, went forward and said to them,
“Whom are you seeking?”
5 They answered Him, “Jesus of Nazareth.”
Jesus said to them, “I am He.” And Judas, who betrayed Him, also stood with them. 6 Now when He
said to them, “I am He,” they drew back and fell to the ground.
7 Then He asked them again, “Whom are you seeking?”
And they said, “Jesus of Nazareth.”

9. VIROLOGY

10. VIROLOGY

11. VIROLOGY

12. VIROLOGY

13. VIROLOGY

14. VIROLOGY

15. VIROLOGY

16. VIROLOGY

17. Viruses
 Definitions:
 Virus- acellular, infectious agent having one or more pieces of
nucleic acids, DNA or RNA but not both; wrapped in a protein coat,
+/- membranous envelope; obligate intracellular parasite
 Bacteriophage (phage)- a virus that infects bacteria
 Viral Replication
 Lytic- replication involves use of the host cell’s organelles and enzymes
to produce virions resulting in the death and lysis of the host cell; results
in cell death
 Lysogenic- viral DNA is inserted into the host genome; it is copied when
the cell replicates and passed to daughter cells; an external stressor can
induce the cell into the lytic phase
 Transduction- transfer of bacterial genes by a phage
 Prophage- insertion of phage DNA into bacterial chromosome

18. Viruses

19. VIRUSES
 Background History
 Discovered in 1892 by Russian botanist Dmitri Ivanosky
 Tobacco mosaic virus (TMV)
 Hershey and Chase- in 1952 demonstrated that DNA is
the genetic material of a bacteriophage (T2) which
infects the bacterium Escherichia coli (E. coli)

20. Viruses

21. Viruses
 Characteristics of Viruses
 Similarities
 Intracellular/extracellular- virion
 Protein Coat- capsid
 Membrane-like envelope- not all

22. Viruses

23. Viruses
 Characteristics of Viruses
 Differences
 Genetic Material
 Classification based on type of genetic material in viral
genome
 Double-stranded DNA (dsDNA)
 Single-stranded RNA (ssRNA)
 Single-stranded DNA (ssDNA)
 Double-stranded RNA (dsRNA)

24. Viruses
 Characteristics of Viruses
 Differences
 Hosts of Viruses
 Most viruses infect only particular host’s cells
 HIV- T helper cells
 Rabies- humans to bats
 Plant viruses- corn, sugarcane, tobacco, tomatoes, beans
 Fungal viruses

25. Viruses
 Characteristics of Viruses
 Differences
 Sizes- 10nm t0 300nm
 Poliovirus 30nm
 Smallpox virus 200nm x 300nm

26. Viruses

27. Viruses
 Characteristics of Viruses
 Capsid Morphology
 Composed of protein subunits- capsomeres
 Viral Shapes
 Helical, polyhedral, complex
 Viral Envelope
 Enveloped vs. Nonenveloped
 Acquired from the host cell during viral replication or release
 Plays a role in the recognition of host cells

28. Viruses

29. Viruses

30. Viruses

31. Viruses

32. Viruses
 Classification
1. Taxonomy
 Type of nucleic acid
 Presence of an envelope
 Shape
 Size

33. Viruses
 Retroviruses
 RNA viruses, +ssRNA
 Require reverse transcriptase to make a DNA intermediary
 mRNA is transcribed from the DNA by RNA polymerase
 DNA is incorporated into the host DNA (provirus)
 Examples-
 Rous Sarcoma Virus- infects chickens
 Simian Immunodeficiency Virus
 Feline Leukemia Virus
 HTLV- 1st human retrovirus discovered
 HIV

34. VIRUSES

35. Viruses
 Impact of Viruses
 Replicate quickly, mutate rapidly, remain hidden inside host
cells
 Antibiotics/Antivirals
 Threat of viral diseases
 Human
 Plant
 Cloning
 Oncogenes
 Burkitt’s Lymphoma- EBV
 Kaposi’s Sarcoma- HHV-8
 Cervical Cancer- HPV
 Hepatocarcinoma- HEP B

36. VIRUSES

37. Viruses
 References:
1. Bauman, R. W., & Timberlake, K. C. (2006).
Microbiology and chemistry: An integrated approach.
Boston, MA: Pearson Custom Publishing.
2. Campbell, N. A. (2009). Biology: Concepts &
connections. San Francisco: Pearson/Benjamin
Cummings.
3. Kasper, D. L., & Harrison, T. R. (2005). Harrison's
principles of internal medicine. New York: McGraw-
Hill, Medical Pub. Division.