Virus Structure, Classification, and Cycles of Infection Lila Tefft, Joe Greger, and Melanie Huot

Overview Viruses Different Viruses Viral Reproduction Definition Structures Identification as living or nonliving Different Viruses Bacteriophage Adenovirus Retrovirus Viral Reproduction Lytic Cycle Lysogenic Cycle Compare and Contrast

What is a virus? Made of proteins and nucleic acids Only reproduces by infecting living cells  Can infect all life forms Differ widely in structure and size Virus attacking cell LT

Visuals of Viruses T4 Bacteriophage Tobacco Mosaic Virus Influenza Virus LT

Structure of Viruses Either has RNA or DNA- information to transmit to host cell Surrounded by CAPSID- Protein coat surrounding genetic material Allows virus to bind to cell LT

Are Viruses Alive? ABILITY TO REPRODUCE GENETIC INFORMATION YES, THEY ARE ALIVE NO, THEY ARE NOT ALIVE ABILITY TO REPRODUCE GENETIC INFORMATION ADAPTS TO ENVIRONMENTS HAS NO CELLS/MADE UP OF MOLECULES CANNOT CREATE ENERGY CANNOT LIVE WITHOUT HOST LT

Bacteriophage Virus infecting Bacteria Composed of a DNA and RNA core with a protein coat Attaches itself to the surface of a cell and injects its Genetic Information throughout Largely distributed across the globe within the Biosphere Makes up most of all living organisms of Earth JG 

Adenovirus Most common Respiratory Illness causing: sore throat Pneumonia Conjunctivitis (pink eye)  Cold-like symptoms such as: headache, coughing, and/or diarrhea Infants most susceptible to adenovirus due to weak immune system  People with a compromised Immune system are susceptible JG 

Retrovirus Single-stranded positive-sense RNA Virus Considered an Obligate Parasite: targets a host cell to exploit it for resources Uses different coding sequence:  RNA → DNA → RNA → Polypeptide Now considered Provirus: New DNA is then incorporated into the host cell genome JG 

Retrovirus (cont.) - Reverse Transcriptase DNA polymerase enzyme that catalyzes the process of Reverse Transcription Enzyme used to generate Complementary DNA HIV uses reverse transcriptase to generate new viruses   Generates a long-term infection  Non-retroviruses widely used as Antiretroviral Drugs JG

The Lytic Cycle Virus will attach to the bacterium, or HOST cell Inject GENETIC material  Reproduce itself Particles assemble selves into NEW viruses Overrun the host cell and break off, LYSING, and killing cell MH

The Lysogenic Cycle Phage attaches to BACTERIUM Inject DNA DNA CIRCULIZES – Incorporates self into GENOME MH 

The Lysogenic Cycle cont. Becomes DORMANT Host cell divides – PROPHAGE passed to daughter cells Phage DNA can SEPARATE from chromosome – enters LYTIC cycle MH

Lytic Cycle versus Lysogenic Cycle Cell and DNA destroyed Virus replicates SEPARATELY Symptoms of viral infection Both Methods of viral reproduction Attach to cell and insert DNA Replicates using HOST Lysogenic PROPHAGE, cell not destroyed No viral symptoms Phage DNA in daughters Can enter LYTIC Cycle MH 

WHAT ARE VIRUSES MADE OF? ABC's WHAT ARE VIRUSES MADE OF? Carbohydrates and proteins B. Proteins and lipids C. Phospholipids D. Proteins and nucleotides LT 

WHAT ARE THE TWO MAIN STRUCTURES FOUND IN VIRUSES? ABC's WHAT ARE THE TWO MAIN STRUCTURES FOUND IN VIRUSES? Mitochondria and nucleus DNA and cell membrane Protein coat and genetic material Chloroplasts and mitochondria LT 

A BACTERIOPHAGE VIRUS INFECTS: ABC's A BACTERIOPHAGE VIRUS INFECTS: Nucleus Bacteria Blood cells Nerve cells  JG

A RETROVIRUS, AKA OBLIGATE PARASITE, IS CONSIDERED A: ABC's A RETROVIRUS, AKA OBLIGATE PARASITE, IS CONSIDERED A: Antiretroviral Virus Provirus RNA Virus  DNA Virus JG

WHEN CAN A VIRUS INSIDE OF A CELL BE DORMANT? ABC's WHEN CAN A VIRUS INSIDE OF A CELL BE DORMANT? Lytic Cycle Before determining which cycle to go through After it has been reproduced Lysogenic Cycle MH 

WHAT IS AN OUTCOME OF THE LYTIC CYCLE? ABC's WHAT IS AN OUTCOME OF THE LYTIC CYCLE? Cell reproduces passing virus to daughter cells Phages overrun and destroy the cell Prophage may leave chromosome Phage DNA is integrated in cell DNA MH

Summary Viruses Different Viruses Viral Reproduction Definition Structures Identification as living or nonliving Different Viruses Bacteriophage Adenovirus Retrovirus Viral Reproduction Lytic Cycle Lysogenic Cycle Compare and Contrast