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Biology · 2026 · 3 marks
CBSE 2026 · Region 4 · Set 2 · Q28
(a) Name the cells of the human body attacked by HIV first, when it gains entry into a human body. How does this virus replicate further to cause…
(a)
Name the cells of the human body attacked by HIV first, when it gains entry into a human body. How does this virus replicate further to cause immunodeficiency in the body ?
OR
(b)
Show with the help of a flow chart only, the life-cycle of malarial parasite in human.
Marking-scheme solution
-HIV attacks Macrophages first.
-RNA genome starts producing viral DNA by reverse transcriptase.
-The viral DNA gets incorporated into the DNA of host cell and directs the infected
cells to produce viral particles.
-The new viruses are released from the macrophages and they start infecting helper
T lymphocytes (TH).
-Progressive decrease in helper T-lymphocytes takes place.
-So the immune system of infected person becomes weak and start suffering from
infections.
Sporozoites are infected into human body by the bite of female Anopheles.
↓
Sporozoites reach in liver cells through blood.
↓
The parasite reproduces asexually in liver and by bursting the liver cells and new cells are released into blood.
↓
Enter into the RBCs and reproduce asexually
↓
Rupture of RBCs and release of haemozoin
↓
New cells of parasite enter new RBCs and undergo gametogenesis to produce male and female gametocytes.
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CBSE Class 12 Biology past-paper question from the 2026 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.