In DNA, each nucleotide is made up of a deoxyribose sugar, a phosphate group and one of four different nitrogenous bases (adenine, thymine, guanine or cytosine).
Each of the two strands in DNA is extremely long, and they are joined together by hydrogen bonds formed between complementary base pairs.
The bases on the two strands of DNA attach via hydrogen bonds to complementary bases on the other strand. Adenine is complementary to thymine, and guanine is complementary to cytosine.
In RNA, adenine is complementary to uracil and cytosine is complementary to guanine.
The quantities of adenine and thymine in DNA are the same, and the quantities of cytosine and guanine are the same.
The structure of DNA can be compared to a double helix ladder, whereby the phosphate groups and deoxyribose sugars form the structural backbone of DNA.
