Question

Given below is a schematic diagram of a portion of DNA.
a) How many strands are shown in the diagram?
b) How many nucleotides have been shown in each strand?
c) Name the parts numbered 1, 2, 3, 4, and 5 respectively.
d) Name the DNA unit constituted by the parts 1, 2 and 3 collectively.

Answer 1

a) Two strands of DNA are shown in the diagram. The two linear strands form the double strands of DNA.

b) Each strand has two nucleotides. The nucleotide is a structure comprising of a nucleoside and a phosphate group linked to it. Nucleoside comprises of a nitrogenous base and a ribose sugar linked together.

c) The part named "1" is a phosphate group, the part named "2" is a ribose sugar. the part named "3" is a pyrimidine, the part named "4" is hydrogen bond which links the pyrimidine and purine. The part named '5" is purine.

d) The part 1 is a phosphate group, the part 2 is a ribose sugar and the part 3 is a nitrogenous base and hence they collectively constitute Nucleotide.