The nucleus of a cell contains chromosomes made of DNA molecules. Each chromosome carries a large number of genes.
In body cells the chromosomes are normally found in pairs.
Recognise/draw/interpret diagrams. Translate from data to a representation with a model. Use models in explanations, or match features of a model to the data from experiments or observations that the model describes or explains. Make predictions or calculate quantities based on the model or show its limitations. Give examples of ways in which a model can be tested by observation or experiment.