Match the following.

	List - I		List - II
A)	Length of the one coil of DNA	i)	0.34 nm
B)	Number of bases in 1 coil	ii)	3.4 nm
C)	Diameter of DNA helix	iii)	20
D)	Rise per base pair	iv)	20 A°

	A	B	C	D
1)	i	ii	iii	iv
2)	ii	i	iii	iv
3)	iv	iii	ii	i
4)	ii	iii	iv	i

 

Watson and Crick B form of DNA dimensions

Salient features :

Double-helix structure of DNA ,diameter of helix is 20A.

 It is made of two polynucleotide chains,

 The bases in two strands are paired through hydrogen bond (H-bonds) forming base pairs (bp)

The two chains are coiled in a right-handed fashion. 

The pitch of the helix is 3.4 nm (height of one turn),10 bp in each turn.

  the distance between a bp in a helix is approximately 0.34 nm.

NCERT Page No.81, 82.