HIV

Question 1

Structural genes

Answer 1

Gag gene
Pol gene
Env gene

Question 2

Gag gene:

Answer 2

Helps to form core of virus.
* Encodes precursor protein p55 which is cleaved by viral protease (p10) to form matrix
protein (p17), capsid protein (p24) & nucleocapsid protein (p7 & p9).

Question 3

Pol gene:

Answer 3

Encodes the precursor protein P100 which is cleaved to form protease (p10), reverse transcriptase, integrase & endo(ribo)nuclease.

Question 4

Env gene

Answer 4

Env gene encodes precursor protein gp160 which is cleaved to form surface spike glycoprotein (gp120) and transmembrane protein (gp41).
* Genetic variety of HIV strain resides in env

Question 5

Non-structural/ regulatory genes

Answer 5

Tat gene
Rev gene
Nef gene
Vif gene
Vpr gene
Vpu gene in HIV-I / Vpx gene in HIV-II

Question 6

Tat gene: ( transactivator of transcription)

Answer 6

Encodes transactivator protein (p14) which promotes transcription of viral genome

Question 7

Rev gene: (regulatory of expression of viral protein)

Answer 7

Encodes Rev protein (p19) and promotes expression of viral structural proteins

Question 8

Nef gene: ( Negative expression factors)

Answer 8

Encodes precursors protein p27
Down regulates expression of CD4 cells, macrophage and MHC-II.

Question 9

Vif gene: (Virion infectivity factor)

Answer 9

Encodes precursor protein p23
Promotes viral infectivity by suppressing inhibitory actions of host cell proteins.

Question 10

Vpr gene:

Answer 10

Encodes precursor protein p15.
Promotes transport of viral pre-initiation complex into nucleus of host cell.

Question 11

Vpu gene in HIV-I / Vpx gene in HIV-II

Answer 11

Encodes precursor protein p16.
Promotes maturity and releases of progeny virus from host cell.

Question 12

• Enzymes:

Answer 12

• Reverse transcriptase (RNA dependent DNA polymerase)
  -integrase
• Protease
• Ligase

Question 13

Reverse transcriptase (RNA dependent DNA polymerase)

Answer 13

convert its RNA into viral DNA

Question 14

Protease

Answer 14

cuts HIV proteins into their functional parts

Question 15

Integrase:

Answer 15

inserts the viral DNA into the cell’s DNA

Question 16

Ligase

Answer 16

catalyzes the joining of two cohesive- or blunt-ended strands of DNA between the 5 ́-phosphate and the 3 ́-hydroxyl groups of adjacent nucleotides.

Question 17

Oncogenic potential:

Answer 17

• High association: Kaposi sarcoma, non-Hodgkin lymphoma &cervical
  cancer.
• Also seen: Cancer of the skin, anus, lung, and liver, Hodgkin lymphoma.

Question 18

Capable of mutation:

Answer 18

• Genetic variation ( HIV 1 &2), new subtypes→difficult to produce vaccines
• Enhances viral infectivity
• Promotes drug resistance

Question 19

Species specific :

Answer 19

• CD4 T cells, macrophages & dendritic cells of humans are the target cells.
• Closely related to simian immunodeficiency viruses SIV, infecting primates