Question

Describe how an HIV particle enters a host cell: Explain the role of the reverse transcriptase in the life cycle of a retrovirus: Explain the significance of the formation of a provirus:

Answer 1

Describe how does HIV enters a host cell. When HIV infects a cell, it first attaches to and fuses with the host cell. Then the viral RNA erton converted into DNA and the virus uses the host cell's machinery to replicate itself during a process called reverse transcription. The new copies of HIV then leave the host cea and move on to infect other cells. Step 4: Reverse transcriptase Step 3: HN's protein coat degrades. HIV's RNA and reverse transcriptase are released into cell cytoplasm DNA ewrites HIV's single-stranded RNA as HV'S Step S: HIV's DNA enters the host cell's nucleus and is then inserted into the DNA of a host cell chromosome. 2: HIV fuses the cell Step 6 Many HIV leaving the host cell Step 7: HIV RNA copies of single-stranded HIV RNA are made. They direct the synthesis of Hiv's proteins. h n and proteins gather at the cell membrane and leave the host cell as an immature releases its contents into the host cell. Reverse HIV RNA HIV RNA HIV DNA Step 1: HIV attaches to a CD4 receptor on the cell membrane of the host cell. HIV provirus Step & HIV RNA and proteins are reassembled to form a mature

Role of reverse transcriptase in the life cvcle of a retrovirus: Retroviruses are RNA-containing viruses that use the enzyme reverse transcriptase to copy their RNA into the DNA of a host cell. Reverse transcriptase is the replication enzyme of retroviruses. Because it polymerizes DNA precursors, reverse transcriptase is a DNA polymerase. However, whereas cellular DNA polymerases use DNA as a template foir making new DNAs, reverse transcriptase uses the single-stranded RNA iin retroviruses as the template for synthesizing viral DNA. This unusual process of making DNA from RNA is called "reverse transcription" because it reverses the flow of genetic information (from DNA to RNA, rather than from RNA to DNA found in transcription). Because reverse transcriptase is essential for retroviruses such as HIV-1 (the virus that causes AIDS), it is the target of many antiretroviral therapeutics.

Explain the significance of the formation of a provirus. A provirus, or prophage, can integrate itself into the host chromosome and lay dormant. The benefit to doing so (lysogenic cycle) is that there may not be enough nutrients outside the cell to support progeny (replicated viruses), or there may not be enough uninfected hosts to support them. Most of the time, a virus cannot enter a cell that already has a prophage incorporated into the genome. Without a host cell, the virus will terminate its life cycle. It is better to remain silent in the host chromosome until the surroundings are favorable. Then, the prophage can enter the lytic cycle, lyse the cell and release its replicated viruses into the surroundings.