7. Secondary Structure of DNA

Question 1

Topic - Secondary Structure of DNA
(Watson-Crick Double Helix Model)

Question 2

DNA is of different types, such as A, B, C, Z, etc.
T/F

Answer 2

True

Question 3

DNA consists of ______ strands arranged ______ (parallel/antiparallel) as a double helix.

Answer 3

Two polynucleotide strands; antiparallel

Question 4

In DNA, a nucleotide consists of -

Answer 4

N-base, deoxyribose sugar, and a phosphate group

Question 5

The backbone of DNA is formed by:

Answer 5

sugar-phosphate-sugar chain

Question 6

Steps are formed of Nitrogen base pairs.
Nitrogen bases include:

Answer 6

Adenine (A), Guanine (G), Thymine (T), and Cytosine (C).

Uracil absent

Question 7

The base pair between purine and pyrimidine (A=T, G ≡ C) takes place such that the diameter of Helix is uniform throughout its length.
T/F

Answer 7

True

Question 8

I. A pairs with T (A=T) by ____ bonds
II. G pairs with C (G≡C) by _____bonds

Answer 8

I. 2 H bonds
II. 3 H bonds

Question 9

A phosphate molecule links ____ atom of the sugar of one nucleotide to ____ of the sugar of the succeeding nucleotide.

Answer 9

3’-carbon atom; 5’-carbon atom

Question 10

a. 1 Nucleoside + Phosphate =
b. 2 Nucleotides =
c. Nitrogen Base + Pentose =

Answer 10

a. 1 Nucleoside + Phosphate = Phospho-ester bond
b. 2 Nucleotides = Phospho-diester bond
c. Nitrogen Base + Pentose = N-glucoside Bond

Question 11

• Structure of DNA

Question 12

Topic: B-DNA or Balanced-DNA

Question 13

One full turn of the helical strand has ____ steps.

Answer 13

10 steps (10 base pairs)

Question 14

Length of one full turn (pitch)=

Answer 14

34 Å (i.e. 3.4 Å for each step)

Question 15

At each step, the strand turns ____.

Answer 15

36°