Transcript Virus
What is a Virus? • Virus: A biological particle composed of nucleic acid and protein • Intracellular Parasites: organism that must “live” inside a host • Not made of cells or organelles • Can’t reproduce on own • Don’t metabolize energy • Don’t perform cellular processes • Reproduce • Have nucleic acid • Adapt to surroundings • Have organization • All Have: – 1) Capsid: coat of protein that surrounds nucleic acid – 2) Nucleic Acid: RNA or DNA • Some Have: – Tail Fibers: Used for attachment (not legs) • Shapes vary Virus Video • Bacteriophages (infect bacteria) are often studied – Replication is similar with many animal viruses 1st Step: Attachment – Virus lands on cell membrane – Virus attaches to a cell receptor – No attachment = No infection » Lock & key analogy endocytosis 2nd Step: Entry – Virus enzyme weakens cell membrane – Genetic material (DNA or RNA) enters host cell 3rd Step: Replication – Virus DNA/RNA uses ribosomes to make virus proteins – Virus proteins created by transcription/ translation Viral DNA Viral RNA Viral Amino Acids Viral Proteins 4th Step: Assembly – New virus proteins are assembled in the cytoplasm 5th Step: Release – Virus enzyme causes cell membrane lyse (burst) – Viruses are released to find new host – Cycle repeats 1st step: Attachment = Same 2nd Step: Entry = Same 3rd step: Replication – Virus DNA combines with cell DNA, and waits • Provirus = cell DNA + viral DNA – Cell divides by mitosis – Each new cell will contain the provirus Host Procell virus DNA Provirus Provirus Provirus Provirus Provirus 4th Step: Assembly Same, except many new viruses are being assembled in many cells 5th Step: Release Same, except many cells burst releasing many more viruses The viral DNA become active and starts making new viral proteins The infected cells burst…releasing the new viruses Retroviruses • RNA viruses • Contains the enzyme Reverse Transcriptase • Steps – 1) Virus RNA enters host cell. – 2) Reverse transcription takes place to make virus DNA – 3) Virus DNA combines with cell DNA (provirus created) – 4) Once active, normal steps of transcription/translation followed. How is HIV contracted? High Risk Activities Low Risk Activities • High risk activities: • Low risk activities: – 1) Sex (oral, vaginal, anal) – 2) Sharing needles (tattoos, piercings, drugs) – 3) Mother to child in womb – 4) Breast milk – 5) Blood transfusions Adults and children estimated to be living with HIV/AIDS as of end 2001 North America 940 000 Caribbean 420 000 Latin America 1.4 million Eastern Europe & Central Asia Western Europe 560 000 1 million North Africa & MiddleEast 440 000 Sub-Saharan Africa East Asia & Pacific 1 million South & South-East Asia 6.1 million 28.1 million Total: 40 million Australia & New Zealand 15 000 What is AIDS? New Exposures to HIV (2006) Gender of those living with HIV (2003) • Acquired Immunodeficiency Syndrome • AIDS results when: – 1) Amount of T-cells drop (200 T-cells per 1mm³ blood) – 2) Multiple symptoms/infections appear • Rash, fever, headache, sore throat, swollen lymph nodes • Therefore, the HIV virus causes the disease AIDS by killing your T-cells Female Transmission of HIV (2006) Male Transmission of HIV (2006) Want more stats? Go to the Centers for Disease Control’s Website http://www.cdc.gov/hiv/topics/surveillance/united_states.htm