DNA Structure

DNA is a polymer that is made up of many nucleotide chains. Each nucleotide is made up of a sugar, a phosphate group and a base.

All nucleotides are identical, except for the base. Each nucleotide can have one of four bases, which are:

  • Adenine
  • Guanine
  • Cytosine
  • Thymine

Base Pairing

The two strands of DNA are chemically linked by hydrogen bonds between pairs of bases. They are always paired in a certain way, which is known as complementary base pairing:

  • Adenine pairs with the thymine (A-T)
  • Guanine pairs with cytosine (G-C)

These nucleotides join together to form long strands by connecting the sugar of one nucleotide and the phosphate of another nucleotide. A DNA molecule consists of two strands that form a twisted double helix. The backbone of each strand is the alternating sugar and phosphate groups.

The Genetic Code

Each cell stores its genetic information in the DNA base sequence, which makes up the genetic code. The sequence of nucleotides determines the genotype.

DNA has four distinct bases: adenine, thymine, guanine, and cytosine. These four compounds are arranged in various sequences throughout each strand of DNA. Around 3 billion pairs of these bases are found in human DNA.

The arrangement of the bases is critical. It functions as a code that instructs cells to produce specific types of proteins. The variations in these proteins distinguish various living organisms, such as a cactus, a gerbil, and two distinct individuals.