Name the calls HIV (Human Immunodeficiency Virus) gains entry in

Subject

Biology

Class

CBSE Class 12

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 Multiple Choice QuestionsShort Answer Type

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Mention two advantages for preferring CNG over diesel as an automobile fuel.

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Write the probable differences in eating habits of Homo habilis and Homo erectus.

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Mention the role of 'genetic mother' in MOET.

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5.

A male honeybee has 16 chromosomes whereas its female has 32 chromosomes. Give one reason.

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6.

Name a free-living and a symbiotic bacterium that serve as bio-fertilizer. Why are they called so?

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7.

Name the calls HIV (Human Immunodeficiency Virus) gains entry into after infecting the human body. Explain the events that occur in these cells.


After infecting the human body the HIV gains entry into the macrophages.

Events that occur in the cells:

i. The virus enters into macrophages where RNA genome of virus replicates to form viral DNA with the help of enzyme reverse transcriptase.
ii. The viral DNA gets incorporated into host cells DNAand directs the infected cell to produce virus particles.
iii. The macrophage continue to produce virus and in this way acts like a HIV factory.
iv. The HIV enters into helper T-lymphocytos (TH ), replicates and produce progeny viruses. The progeny viruses released in the blood attacks other helper T-helper lymphocytes. This is repeated heading to a progressive decrease in the number of helper
v. Tlymphocytes in the body of infected person. During this period the person suffers from bouts of fever, diarrhoea and weight loss. 
vi. The decrease in the number of the T helper cells leads to infections as the immune system of the person becomes weak. 

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8.

Explain the relationship between CFCs and Ozone in the stratosphere.

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9.

Why are sacred groves highly protected ?

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10.

Following are the features of genetic codes. What does each one indicate ? [2]
Stop codon; Unambiguous codon; Degenerate codon; Universal codon.

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