DNA and the Genome

The genetic material in the cell is made up of a chemical called DNA (deoxyribonucleic acid).

The structure of DNA

DNA is a polymer, which is made up of many smaller units called nucleotides. A chain of nucleotides forms two linear strands. The two strands twist around each other to form a ladder structure called a double helix. This double helix structure is held together by weak hydrogen bonds.

DNA is tightly packaged into thread-like structures called chromosomes, which are located in the nucleus of cells. The nucleotides that make up DNA are arranged to form a genetic code, which determines the characteristics of living organisms.

The Genome

The genome is the entire genetic material of an organism. It contains all the information needed to make the organism. In humans, this includes all 46 chromosomes found in the nucleus of diploid cells. This does not include sex cells, which only have half of a person’s genome.

  • Scientists have worked out the entire human genome, so they know the whole code that our DNA holds


A gene is a small section of DNA that is found on a chromosome. Each gene codes for a particular sequence of amino acids. When these amino acids are arranged, they form proteins. There are only 20 different types of amino acids, but they can be arranged in many different sequences. This means the different combinations can make thousands of different proteins.

The DNA determines which proteins the cell produces, so it determines what the cell will be.

The Human Genome Project

The human genome project is responsible for mapping out the entire human genome. The project holds great importance in understanding diseases and illnesses, which is useful in medical research. Genomes hold many secrets, and studying them is useful for:

  • Identifying genes that are linked to specific types of diseases
  • Understanding inherited disorders and their treatments
  • Tracing human migration patterns from the past