The force that holds DNA together in a double helix is:

1. The force of the twist                   

2. Covalent bonds

3. Ionic bonds or ionic interactions   

4. Hydrogen bonds

In the DNA molecule

1. the total amount of purine nucleotides and pyrimidine nucleotides is not always equal

2.  there are two strands, which run parallel in the 5’ → 3’direction

3. the proportion of adenine in relation to thymine varies with the organism

4. there are two strands, which run antiparallel-one in 5’ → 3’ direction and other in 3’ → 5’

Column-I                                               Column-II
I. Genome of ϕ 174 bacteriophage           A. Ribozyme, RNAase
II. Purine                                               B. 5386 Nucleotides
III. Catalytic RNA                                   C. Adenine and Guanine
IV. Any chemical change in DNA              D. Mutation
The correct match is:
1. I - D, II - B, III - A, IV - C                 

2. I - B, II - A, III - D, IV - C

3. I - D, II - C, III - A, IV - B                 

4. I - B, II - C, III - A, IV - D

The DNA molecule takes a complete turn after

1.  Every base pair

2.  Every five base pairs

3.  Every ten base pairs

4.  Every two base pairs

Distance between two consecutive nucleotide pairs of DNA is

1.0.34nm

2.34angstrom

3.3.4 micrometre

4.34nm

Characteristic(s) of most DNA is / are:
A. A pairs with T by 2 hydrogen bonds.
B. Antipolarity of complementary chains
C. 20Aº diameter
D. 10 bps/turn 
1. A, C                 

2. A, B, C, D                     

3. B, C, D                 

4. A, B, C

Which of the following is not a feature of the double helix model of DNA ?

1. The two chains have anti-parallel polarity

2. A purine always comes opposite to a pyrimidine

3. The pitch of the DNA is 3.4 nm

4. The two chains are coiled in a left handed fashion

Antiparallel strands of a DNA molecule means that:

1. one strand turns anti-clockwise

2. the phosphate groups of two DNA strands, at their ends, share the same position

3. the phosphate groups at the start of two DNA strands are in opposite position (pole)

4. one strand turns clockwise

Which one of the following pairs of nitrogenous bases of nucleic acids is wrongly matched with the category mentioned against it?

1. Thymine, Uracil - Pyrimidines
2. Uracil, Cytosine - Pyrimidines
3. Guanine, Adenine - Purines
4. Adenine, Thymine - Purines

Which among the following characteristics confers
stability to the DNA helical structure?

i.  Presence of Uracil.

ii. Plane of one base pair stacking over the other in
    DNA helix.

iii. Left handed fashion coiling of DNA helix.

iv. Presence of hydrogen bonds.

1. i and ii

2. ii and iii

3. iii and iv

4. ii and iv