Question

Describe (absolutely no pictures) the life cycle of a retrovirus.

Answer 1

Retrovirus is a family of the enveloped viruses that replicate in a host cell thorugh a process called reverse transcription . Retrovirus is sisgle strandard positive sense RNA virus with DNA intermediate and as an obligate parasite targets the host cell

structure of the Retrovirus ;

virions of the retrovirus consists of the enveloped particles about 100 nm diameter .These virions also contain two identical single strandard RNA molecules 7-10 kb in length .the main componts include

Envelope ; composed of the lipids and glycoprotein ,It has three disticnt functions protection from the envinorment via lipid bilayer ,enabling the retrovirus to enter /exit from the host cell through the endosomal memberane trafficking and ability to directly enter cells the fusing the memberanes .

RNA ; It consists of the dimer RNA ,It has the cap at the 5 prime end and poly A tail at the 3 prime end . The RNA genome also has the terminal non coding regions

proteins ; include GAG [group specific antigen] , protease ,poL proteins , and env proteins .

LIFE CYCLE ;

The retroviral life cell begins at the nuclues of the infected cell ,At this stage of the life cycle ,the retroviral genome is a DNA element integrated into and covalently attached to the DNA of the host cells . The genome of the virus is approximately 8-12 kB of the DNA .full length genomic mRNA is made intiating at the 5 prime long terminal repeat . the free particle can now infect new cells by binding to the cell surface receptor . the specificity of the virus cell interaction is determined largly by the envelope of the proteins of the retrovirus . infection leads to the injection of the viral proteins core .

Once inside the cell , the nuclear protein complexes acesses the intracellular DNA nuclotide triphosphate pools , where upon the reverse transcriptase protein intiates creations of double strandard DNA copy of the genome of virus in preparation of integration into the host cell chromosome . upon of the completion of the reverse transcription ,the viral enzyme integrase searches the DNA ,clips the host DNA and sews the double strandard DNA into host cell .the virus now is prepared to intiate a new round of replication