Viruses

Are composed of a core of DNA or RNA surrounded by a ______________. Viruses Viruses Are ___________ Can NOT reproduce by themselves, but replicate with the help of a _______ Are composed of a core of DNA or RNA surrounded by a ______________. NOT CELLS HOST PROTEIN COAT

Yes No Yes No Yes Yes Yes Characteristic of life CELL VIRUS Contain specialized organelles Obtain & use energy Reproduce Contain RNA or DNA Yes No Yes No Only inside a living cell (host) Yes Yes Yes

NO! So, are viruses alive? But viruses can cause disease in _______ kind of living organism—animals, ______, fungi, protists, and bacteria. Ex. A _______________ is a virus that infects bacteria. EVERY PLANTS BACTERIOPHAGE

Structure of a Virus ___________ (outer part of the protein coat) ________(inner part of the protein coat) _____________ (either DNA or RNA) ENVELOPE ENVELOPE CAPSID NUCLEIC ACID NUCLEIC ACID CAPSID

How are viruses identified? A virus is often identified by which type of _______ it has. Ex:_________, plant, or ___________ virus They can also be identified by: - ______ - Type of nucleic acid - Structure of the capsid HOST ANIMAL BACTERIAL SHAPE

Helical Binal Polyhedral

TWO METHODS OF VIRAL REPRODUCTION: Lytic Cycle & Lysogenic Cycle

Lytic Cycle (rapidly kills host cell) Virus ________ its nucleic acid into a cell Viral DNA or RNA __________ the host cell to make new viruses The cell breaks apart – “______” – killing the host cell and __________ new viruses Released viruses are now ready to _______ other host cells INJECTS INSTRUCTS LYSES RELEASING INVADE

1 2 3 4 5

Cell before infection… …and after. Cell before infection…

Lysogenic Cycle The virus does _____ ______________ kill a host cell. The injected viral DNA ______________ into the host chromosome and remains _____________ for a period of time (sometimes years). It becomes ___________ later when it enters the lytic cycle. NOT IMMEDIATELY INTEGRATES HARMLESS HARMFUL

Diseases Caused by Viruses Effect on Body Transmission _________________ Sneezing, sore throat, fever Contact with contaminated objects; droplet inhalation Body aches, fever, congestion, fatigue Noncancerous growths on the skin Contact with warts Helper T cells (immune system) destroyed Contact with contaminated blood or body fluids Fever, red itchy rash Contact with rash; droplet inhalation COMMON COLD INFLUENZA (FLU) WARTS AIDS CHICKEN POX

WARTS CHICKEN POX

Viruses are Specific to their Hosts They can only attack __________cells Not all viruses can pass between different___________(though some can). Ex. _________ can be passed from animal to human. SPECIFIC SPECIES RABIES

Viruses are Specific to their Hosts COLD The common _________ is a virus that specifically attacks _________ of the respiratory tract causing coughing, sneezing and sniffling. Other viruses __________ other types of cells. HIV virus specifically attacks __________ cells of the __________ system. CELLS ATTACK T4 HELPER IMMUNE

PREVENTION & VACCINATION Viruses usually cannot be _______ with medicine, but many viral diseases can be _____________ by Practicing good ____________ Making good ____________ Getting __________________ KILLED PREVENTED HYGEINE CHOICES VACCINATED

Vaccination: Injecting a person with a ______________ or inactivated version of the virus. This stimulates the __________ system to ___________ the virus if it ever enters the body again. Remember, antibiotics kill ONLY ______________. WEAKENED IMMUNE ATTACK BACTERIA

Q: What kingdom of life are viruses in? A: None! They are not alive.