Answer:
Spring can be considered as backbone of the DNA.(as picture is missing there)
Explanation:
In DNA double helical model two main structure are there-
1- Backbone consist of phosphate group and the pentose sugar. It is like two vertical columns of a ladder. In helical structure two complementary stands are there one is 3' to 5' and another one is 5' to 3'.
2- Nitrogenous bases are like horizontal bars of ladder attaching two vertical strands. There are 4 kinds of nitrogenous base ADENINE , THYMINE , GUANINE , and CYTOSINE. One more nitrogenous base URACIL is also there but found in RNA not in DNA.
DNA is made of nucleotide and a nucleotide molecule is made of pentose sugar(deoxyribose) ,phosphate group and nitrogenous base.
