How do nucleotides form DNA?
DNA is just a pattern made up of four different nucleotides . Each nucleotide consists of a sugar (deoxyribose) in the middle of a phosphate group and a nitrogenous base.
Nucleotides form a pair in a molecule of DNA where two adjacent bases form hydrogen bonds. The nitrogenous bases of the DNA always pair up in specific way, purine with pyrimidine (A with T, G with C), held together by weak hydrogen bonds.
The four bases in DNA's alphabet are:
adenine (A) - a purine
cytosine(C) - a pyrimidine
guanine (G) - a purine
thymine (T) - a pyrimidine
Strands of DNA are made by joining sugar and phosphate as backbone (by phosphodiester bonds): two such DNA strands run antiparallely forming the sides of a ladder and the paired bases act as the rungs of the ladder. The molecule appears as a twisted ladder and is called a double helix.
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