Fill in the blanks :
(i) According to Watson and Ctick model, the DNA molecule consists of ............... long, parallel strands. The two strands are .............. around a common axis in a regular manner to form a ........... helix.
(ii) These strands are made of ............ units. Each such unit consists of .......... , ......... and .............
(iii) In each chain, nitrogenous base molecules are joined to the sugar molecules by ............ bonds and project into the space enclosed in the helix at about .......... to the long axis of the helix.
(iv) The nitrogenous bare may be a 9-membered, double ringed ....... or a 6-membered, single ringed .......
(v) The double helix of DNA has a constant diameter of ......... and one complete spiral (turn) of the helix is .......... long and has ........ base pairs.
(vi) The mode of DNA replication is ...........
(vii) Enzyme ............ cannot initiate the synthesis of a new DNA strand, although it can catalyze the growth of a DNA chain. Therefore, a short chain of .......... is formed on the DNA template at the 5' end. This is called ........
(viii) During DNA replication, one new strand is formed in continuous stretch in the 5' - 3' direction. It is called ........... strand. Other strand is formed in small fragments called .......... which are later joined to form a continuous strand termed ............ strand.

Explanation

(i) two, spirally coiled, double
(ii) deoxyribonucleotide, phosphate, deoxyribose sugar, nitrogenous base.
(iii) glycosidic, `90^(@)`
(iv) purine, pyrimidine
(v) 2 nm (20 Å), 3.4 nm (34 Å)
(vi) semiconservative.
(vii) DNA polymerase, DNA, RNA primer.
(viii) Leading, Okazaki fragments, lagging.