THE GENETICS OF VIRUSES Daniela, Shanayah, Nisma

Virus- a small infectious agent that replicates only inside the living cells of other organisms Viruses are acellular organisms Consist of: -Genetic material (double or single-stranded DNA/RNA) -Capsid (protein shell)

General “Obligate intracellular parasites” (Fox, 2011) (Carter, 1997) Can only reproduce with a host cell Don’t have cell machinery

Viruses Composed of a capsid, genetic material, a tail, and base fibers (BBC, 2014 Bacteriophages- virus that infects bacteria specifically (BBC, 2014)

Bacteriophages Lytic cycle: early & late stages Uses promoter for transcription Turns off host gene expression Replicates viral genes Viral genes transcribed and release (Hillis et al., 2012) (Kometani & Matsui, 2005)

Common Viruses: HIV ( Al-Aulfi, 2011) Human Immunodeficiency Virus Retrovirus Causes AIDS Attacks T-helper cells Uses reverse transcriptase to turn RNA into DNA Opportunistic infections (Hillis et al., 2012)

Common Viruses: Rhinovirus (Virology, 2014) Common Cold Attacks respiratory tract Many different strains Symptoms: Runny nose Sneezing Congestion Cough Sore throat

Overview of Viral Replication Two Processes: Lytic Cycle and Lysogenic Cycle Lytic cycle is faster than Lysogenic Lytic cycle, lysogenic cycle, or both can be used for viral replication

Lytic Cycle Lytic Cycle- viruses are made within a host cell, which then bursts open, releasing new viruses Destruction of host cell and membrane  lysis Viral products released Millions of copies in hours Viral genetic material stays in cytoplasm

Lysogenic Cycle Lysogenic –viral DNA is added to the host cell's DNA and is copied along with the host cell's DNA Genetic recombination Viral DNA passed on to daughter cells Doesn’t kill host cell

Matching 1.Bacteriophage 2.Capsid 3.Lytic cycle 4.Lysogenic cycle 5.Acellular 6.Retrovirus 7.Opportunistic infections A.Single-celled B.A virus that infects and replicates within a bacterium C.The protein shell of a virus D.Possesses reverse transcriptase E.infections that usually do not cause disease in a healthy host F.a viral reproductive cycle in which copies of a virus are made and released in lysis G.a viral reproductive cycle in which the viral DNA genetically recombines to the host cell's DNA