The structure of DNA consists of groups called nucleotides which are linked together. A nucleotide contains three parts; a 5-carbon sugar, a phosphate group and a nitrogenous base. The structure of DNA resembles a ladder, the backbone or sides of the ladder contain deoxyribose sugar and a phosphate group bonded together by covalent bonds. The rungs of the ladder are made up by nitrogenous bases. The four bases are adenine, thymine, guanine and cytosine. Adenine and thymine are always paired together and guanine and cytosine are always paired together. They are known as complementary base pairs. The two sides of the ladders are connected by hydrogen bonds which are in-between the n-bases. When the two strands are connected it twists to form a double helix.


The significance of the structure of DNA is contributed firstly by its shape. The DNA is twisted in a double helix, the way it is twisted assists in the process of unzipping the DNA strands. With its unique shape, the DNA does not get knotted or stuck, meaning that it can unzip and can be zipped up with its complimentary strand smoothly without problems. Also, the "backbone" of the DNA (including the phosphate group and the deoxyribose sugar) is held together by covalent bonds. Covalent bonds are difficult to break, meaning that the DNA is kept and held quite tightly. Furthermore, the bases of the DNA are held together with its complimentary bases of the other DNA strand by hydrogen bonds, which are much easier to break. This is because the DNA must keep unzipping so that the mRNA can attach itself to the DNA. Hydrogen bonds help in making this process easier and faster, because these specific bonds are much easier to break.