Watson and Crick described DNA model with certain features that are mentioned below:
DNA is a two-chain structure where purine is opposite to pyrimidine. Both the chains are joined together by H-bonds. Adenine (A), which is a base, is paired with Thymine (T) and they are joined by two H-bonds. In a similar manner, Cytocine (C) is paired with Guanine (G) by three H-bonds. This simply means that if you know the sequence of bases of one strand then you can write the sequence of the other strand. The arrangement of these bases in strands are said to be complementary. This feature describes how a cell can replicate a DNA molecule to make two identical copies of DNA. In addition, Watson and Crick model of DNA also fulfills Chargraff’s Law of DNA that states that the amount of Adenosine in any DNA sample must always equal to the amount of Thymine.
DNA structure consists of two chains of repeating nucleotides. A nucleotide consists of three basic components including a phosphate group, 2-deoxyribose sugar and a nitrogen having bases such as A, T, G, and C.
There are different forms of DNA molecule, however, the model that Watson and Crick described was in the B form. Other forms of DNA are A, C and Z. The basic difference between these forms is the direction that the helix spirals, for example, A, B, and C are right handed helix whereas, Z is a left-handed helix. B is the most commonly found structure that is present in the cell.