Subject

Biology

Class

CBSE Class 12

Pre Boards

Practice to excel and get familiar with the paper pattern and the type of questions. Check you answers with answer keys provided.

Sample Papers

Download the PDF Sample Papers Free for off line practice and view the Solutions online.
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 Multiple Choice QuestionsShort Answer Type

21.

Explain any three advantages that seeds offer to angiosperms.

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22.

Name and explain the role of the inner and middle walls of the human uterus.

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23.

A colour-blind child is born to a normal couple. Work out a cross to show how it is possible. Mention the sex of this child.

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24.

Mendel published his work on inheritance of characters in 1865, but it remained unrecognized till 1900. Give three reasons for the delay in accepting his work. 

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25.

Women are often blamed for producing female children. Consequently, they are ill-treated and ostracized. How will you address this issue scientifically if you were to conduct an awareness programme to highlight the values involved?

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26.

Name the tropical sugar cane variety grown in South India. How has it helped in improving the sugar cane quality grown in North India?

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27.

Identify ‘a’, ‘b’ and ‘c’ in the following table:


No.

Crop

Variety

Insect Pests

1.

Brassica

Pusa Gaurav

(a)

2.

Flat bean

Pusa Sem 2
Pusa sem 3

(b)

3.

(c)

Pusa Sawani
Pusa A-4

Shoot and fruit borer

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28.

Why are beehives kept in a crop field during flowering period? Name any two crop fields where this is practiced.

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29.

How did the process of RNA interference help to control the nematode from infecting the roots of tobacco plants?

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30.

Explain the process of DNA replication with the help of a schematic diagram.


DNA replication is the phenomenon in which a duplicate copy of DNA is synthesized

The steps involved in the process of DNA replication are as follows:

i) DNA replication occurs in S-phase of the cell cycle.

ii) Enzyme involved: DNA polymerase (DNA-dependent DNA polymerase)

iii) Replication requires energy

Source of energy -Deoxyribonucleoside triphosphates (dNTPs)

dNTPs have dual purposes: act as substrates as well as provide energy

Replication initiates at specific regions in DNA called the origin of replication.

DNA polymerase polymerises a large number of nucleotides in a very short time.

During the course of replication, two parent strands do not completely open, but a small opening form in which replication occurs. This small opening forms a replication fork.

DNA polymerase can polymerize only in one direction, i.e,'

Therefore, replication occurs smoothly into end of DNA (continuous replication, but occurs discontinuously into end).

The discontinuous fragments so formed are joined by DNA ligase

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