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. Capsid3. Lytic cycle4. Lysogenic cycle5. Acellular6. Retrovirus7. Opportunistic

infections

A. Single-celled B. A virus that infects and

replicates within a bacterium C. The protein shell of a virusD. Possesses reverse transcriptaseE. infections that usually do not

cause disease in a healthy hostF. 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