1 / 36

Viruses

Viruses. Objective: Explain reverse transcription and how retroviruses use it during infection, as well as how it is used in biotechnology. Task: Please copy two key definitions into your notes: Reverse Transcription : making a dsDNA molecule from an RNA template

ellema
Download Presentation

Viruses

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Viruses Objective: Explain reverse transcription and how retroviruses use it during infection, as well as how it is used in biotechnology. Task: Please copy two key definitions into your notes: Reverse Transcription: making a dsDNA molecule from an RNA template Gene splicing: inserting DNA from one organism into another. The result is a transgenic organism

  2. Ebola Zaire • Most lethal viral infection known to science ( > 85% of cases fatal) • Antisense ssRNA virus (ss = singlestranded) • 19 kbp genome (human = 3.1 Gbp) codes for 8 proteins

  3. Today’s Big Ideas • Viruses are small genetic entities that are obligate pathogens. (the only way they can survive is through other cells) They are not cells, and contain no ribosomes. • Most viruses defy the normal rules of DNARNAProtein, • some of them store information as RNA • Some can perform reverse transcription • High diversity and mutation rate • Virus may follow a lytic lifecycle or a lysogenic one • Lytic cycle = makes new viruses directly • Lysogenic cycle = inserts genetic info into host.

  4. The Lytic Cycle: viral genes translated immediately

  5. Lysogenic Cycle: viral RNA reverse transcribed into host DNAex: HIV, HPV, others

  6. Important Characteristics • RNA virus • H & N refer to different versions of viral proteins. • ~100 nm (0.1 μm) diameter. spherical

  7. Transmission: Aerosol or hand-mouth

  8. Step 1: Hemagglutinin Protein Binds to Epithelial Cell in Nose or Lungs H Protein Lung Cell

  9. Hemagglutinin • http://biology.kenyon.edu/BMB/Chime2/2005/Cerchiara-Holsberry/FRAMES/start.htm

  10. Step 2: Endocytosis of Virus by Cell

  11. Step 2: another view

  12. Step 3: Viral Genes Enter Cytoplasm

  13. Step 4: vRNA Enters Nucleus, Begins making virus materials • vRNA and vRNA polymerase begin replicating and transcribing the virus genes. • Viral genes are transcribed by host cell ribosomes, producing proteins that take over the cell: • Break down cell mRNAs for parts • Use the nucleotides to copy genetic material • Build proteins with cell ribosomes for new viruses

  14. Step 5: Virus Assembly

  15. Step 6: Release of Viruses

  16. 6 Steps of Viral Infection • Attachment • Endocytosis • Unpackaging • Viral Synthesis • Assembly • Release

  17. Human Immunodeficiency Virus: HIV Do Now: Begin reading the background information about HIV/AIDS. We will complete flu presentations momentarily.

  18. 9 genes, 19 proteins, 2.5 million deaths per year.

  19. Where HIV Strikes

  20. Who HIV Strikes: High Risk Behaviors *Includes persons with a diagnosis of AIDS from the beginning of the epidemic through 2007.**Heterosexual contact with a person known to have, or to be at high risk for, HIV infection.*** Includes hemophilia, blood transfusion, perinatal exposure, and risk not reported or not identified.

  21. HIV Demographics

  22. US Demographics

  23. RNA Virus • HIV stores its genes in the form of RNA. Each free virus has 2 identical copies of the same molecule.

  24. HIV is a Retrovirus • A retrovirus is a type of virus which inserts its genetic material into the DNA of the host cell it infects. • Because the viral genes become part of cell’s own DNA, it is nearly impossible to completely get rid of an HIV infection. • This is also the reason HIV infection may take 10-15 years to cause AIDS

  25. STEP 1: Gp120 protein on virus attaches to CD4 protein on white blood cell

  26. STEP 2: Reverse Transcriptase makes DNA copy of vRNA vRNA DNA-RNA Hybrid Molecule Reverse Transcriptase

  27. Reverse Transcription: A Powerful Tool for Humanity & Viruses • Remember that transcription is the process by which a cell makes an RNA copy of a gene stored as DNA. The RNA molecule produced provides the instructions for protein synthesis to the ribosomes.

  28. Transcription: Forward and Backwards • Transcription: DNA  RNA • Reverse Transcription: RNA  DNA • REVERSE TRANSCRIPTION is the process by which a DNA copy of an RNA molecule is made. • The ability to make double stranded DNA from single stranded RNA is how retroviruses insert themselves into host DNA • It is also a key tool of biotechnology, allowing for the study and storage of all genes being expressed in a cell.

  29. STEP 3: Integrase inserts DNA copy of viral genes into host DNA. Integrase protein Virus DNA Host DNA

  30. STEP 4: Proviral DNA is transcribed into mRNA. Host DNA Proviral mRNA proviral DNA

  31. STEP 5: Viral Proteins are made and processed Protease Viral pre-protein Finished viral protein

  32. STEP 6: Viral RNA and proteins assemble into a capsid Protease Viral RNA Reverse Transcriptase

  33. Step 7: New virus buds from cell

More Related