MCAT Content / Viral Life Cycle / Retrovirus Life Cycle Integration Into Host Dna Reverse Transcriptase Hiv

Retrovirus life cycle: integration into host DNA, reverse transcriptase, HIV

Topic: Viral Life Cycle

Retroviruses, like HIV, have single-stranded RNA and contain reverse transcriptase to convert it to double-stranded DNA to integrate it into host DNA.

Retroviruses, like the human immunodeficiency virus (HIV) that causes AIDS, are a unique class of viruses. The genetic material of retroviruses is single-stranded RNA with two copies per viral particle. The RNA must be converted into double-stranded DNA by an enzyme called reverse transcriptase. It is fittingly named, as it reverses the normal flow of DNA to RNA to protein in cells; instead, it converts single-stranded viral RNA to double-stranded DNA. The double-stranded DNA enters the nucleus of the host cell and is inserted into the host genome by an enzyme called integrase. mRNA can then be made by transcription of the viral DNA, which, as a permanent part of the host cell’s genome, is called a provirus. The mRNA is read to produce viral proteins using the host cells ribosomes to make new viral particles that assemble and bud from the cell.


Practice Questions

 

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Key Points

• HIV, which causes AIDS, is a retrovirus

• Retrovirus’ genetic material is single-stranded RNA, which must be converted to double-stranded DNA by reverse transcriptase.

• Integrase then fuses the viral DNA into the host genome permanently. The integrated viral genetic material is now known as a provirus.

• mRNA can be made from the provirus to made new virions.


Key Terms

retrovirus: a type of RNA virus that integrates its genome into the DNA of its host cell

HIV: a retrovirus that causes acquired immune deficiency syndrome (AIDS)

reverse transcriptase: a viral protein that converts single-stranded RNA to double-stranded DNA

integrase: a viral protein that integrates viral DNA into the host genome

provirus: viral DNA that is permanently fused into the host genome

AIDS: Acquired immunodeficiency syndrome is caused by the human immunodeficiency virus (HIV) damaging the immune system

genome: the whole of an organisms hereditary information encoded in its DNA

RNA: is a single-stranded RNA molecule that is read by a ribosome to produce a protein

ribosomes: organelles that carry out protein synthesis.



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