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Lecture 9

MCDB 21 Lecture Notes - Lecture 9: Lysogenic Cycle, Lytic Cycle, Reverse Transcriptase


Department
Molecular, Cellular & Develop. Biology
Course Code
MCDB 21
Professor
SH Low
Lecture
9

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Lecture 9 (5/2/19)
HIV is a retrovirus
- HIV RNA → reverse transcriptase DNA copy → provirus → HIV RNA
- Normally: DNA → RNA → protein
Steps in general viral replication
- Union of virus & host cell (adsorption)
- Penetration & uncoating
- Nucleic acid synthesis
- Viral protein synthesis
- Assembly of new viruses
- Release of new viruses
Lytic vs. Lysogenic Cycle of Bacteriophage
- Lysogenic cycle → phage DNA integrated into a prophage
- Cell division keeps replicating this
- Prophage can excise itself from host chromosome & enter the lytic cycle
- Lytic cycle → replication of viral genome formation of phages that lyse the cell
Latent Infection/Lysogeny
- Lysogeny → latent infection → virus exists as a provirus in the nucleus & does not
replicate
- Evidence that HIV provirus can begin producing new copies of HIV RNA immediately
after becoming a provirus or shortly thereafter
HIV in Lysogenic cycle = latent infection
- HIV DNA is integrated into the host cells chromosome as a provirus
- Patient does not have AIDS, but has HIV infection
- Good health but is infectious
- Provirus can be transmitted via infected T cells in blood, semen, & vaginal secretions
Drug targets for inhibiting HIV replication
- Block entry of HIV into host cell by blocking CD4 and or co receptors
- Inhibit reverse transcriptase because only HIV has this enzyme
- Inhibit integrase so HIV cannot integrate
- Inhibit protease so HIV cannot process its proteins into functional subunits
Function of Co-Receptors
- CXCR4 and CCR5 proteins are chemokine receptors
- Chemokines:
- Secreted chemoattractant proteins
- Small proteins similar to cytokines
- Produced during an inflammatory reaction
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