DNA Structure
- DNA, or deoxyribonucleic acid, is the molecule that contains the instructions for the growth and development of all organisms
- It is found in the nucleus of cells in structures called chromosomes
DNA and chromosomes diagram
DNA, chromosomes and the nucleus
- The individual units of DNA are called nucleotides
Nucleotide diagram
A nucleotide is made up of several components to form the overall structure of DNA
- The double helix shape is formed from two strands of DNA wound around each other, like a twisted ladder
- The phosphate and sugar section of the nucleotides form the ‘backbone’ of the DNA strand (like the sides of a ladder) and the base pairs of each strand connect to form the rungs of the ladder
DNA double helix diagram
The DNA helix is made from two strands of DNA held together by hydrogen bonds
- It is the sequence of nucleotide bases that determines the order of the amino acids used to form different proteins
- Therefore the proteins produced by a cell are dependent on the DNA
Examiner Tip
If you are not sitting the higher tier qualification, you do not need to learn the names of the bases, just their letter. Make sure you know which bonds with which, as this is the most commonly asked question about this topic.