Basic units of inheritance are known as genes. Every cell in the human body contains approximately 25 000 genes. Genes are passed down from parents to offspring and contain DNA sequences which carry coded information that instructs the growth, development and function of the human body. DNA is essentially the blueprint of health and disease. Mutations or errors in DNA can be passed down from parents to offspring and can sometimes cause disease or increase an individual’s susceptibility to disease.
Traditionally, the practice of genetics has been concerned with conditions or diseases such as cystic fibrosis or Huntington disease that are caused by mutations in single genes. However, as the focus on genetics and single genes is shifting towards multiple genes and gene-environment interactions (genomics and epigenetics), our understanding of the more complex multifactorial genetic disorders, such as cancer and diabetes, is increasing. This has resulted in a more mainstream approach to the application of genetics and genomics to a wide variety of clinical problems in the healthcare setting.