Genetic inheritance is the passing of traits from parents to their offspring through the transfer of DNA. Offspring inherit half of their DNA from each parent. Each gene in DNA provides the instructions for a specific trait. These instructions are expressed as proteins, which determine an individual's physical characteristics. Dominant genes are expressed even if only one parent passes them on, while recessive genes are only expressed if both parents pass them on. Genetic mutations can also occur spontaneously or be inherited, leading to genetic disorders.