viruses
DESCRIPTION
Viruses . Lytic vs. Lysogenic . Vaccines. First made was in 1700’s- fight smallpox Help prevent viral infections, but they cannot cure most viral infection Some recently-developed drugs do combat some viruses, mostly by interfering with viral nucleic acid synthesis. - PowerPoint PPT PresentationTRANSCRIPT
VIRUSES
Lytic vs. Lysogenic
Vaccines• First made was in 1700’s- fight smallpox• Help prevent viral infections, but they cannot cure most
viral infection • Some recently-developed drugs do combat some viruses,
mostly by interfering with viral nucleic acid synthesis.• AZT interferes with reverse transcriptase of HIV.• Acyclovir inhibits herpes virus DNA synthesis.
WHAT IS HIV??• “Human Immunodeficiency Virus”• A unique type of virus (a retrovirus)• Invades the helper T cells in the body of the host• Preventable, managable but not curable
WHAT IS AIDS ???• “Acquired Immunodeficiency Syndrome”• HIV is the virus that causes AIDS• Disease limits the body’s ability to fight infection due to reduced helper T cells.
• Patients predisposed to multiple opportunistic infections leading to death.
Stage 1 - Primary• Short, flu-like illness - occurs one to six weeks after infection
• Mild symptoms• Infected person can infect other people
Stage 2 - Asymptomatic• Lasts for an average of ten years • This stage is free from symptoms• There may be swollen glands• The level of HIV in the blood drops to low levels
• HIV antibodies are detectable in the blood
Stage 3 - Symptomatic
• The immune system deteriorates • Opportunistic infections and cancers start to appear.
Stage 4 - HIV AIDS
• The immune system weakens too much as CD4 cells decrease in number.
Opportunistic Infections associated with AIDS• Bacterial infections
• Tuberculosis (TB)• Herpes Simplex• Herpes Zoster• Vaginal candidiasis• Hairy leukoplakia• Kaposi’s sarcoma
Opportunistic Infections associated with AIDS
• Pneumocystic carinii• Toxoplasmosis• Cryptococcosis• Coccidiodomycosis• Cryptosporiosis• Non hodgkin’s lymphoma
HAART = highly active anti-retroviral treatment
Transduction
• Definition: Gene transfer from a donor to a recipient by way of a bacteriophage
Transduction
• Types of transduction– Generalized - Transduction in which
potentially any donor bacterial gene can be transferred
Generalized Transduction
• Release of phage
• Phage replication and degradation of host DNA• Assembly of phages particles
• Infection of recipient• Legitimate recombination
• Infection of Donor
Transduction• Types of transduction
• Generalized - Transduction in which potentially any dornor bacterial gene can be transferred.
– Specialized - Transduction in which only certain donor genes can be transferred
Specialized TransductionLysogenic Phage
• Excision of the prophage
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bio
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• Replication and release of phage
• Infection of the recipient
• Lysogenization of the recipient– Legitimate
recombination also possible
Transposable Genetic Elements• Definition: Segments of DNA that are able to move from
one location to another• Properties
• “Random” movement• Not capable of self replication• Transposition mediated by site-specific recombination
• Transposase
• Transposition may be accompanied by duplication