Genetic conditions can be inherited in a number of ways. A Geneticist or Genetic Counsellor will be able to tell you more about how these inheritance patterns apply to your personal situation.
Autosomal Dominant Inheritance information leaflet
Autosomal Recessive Inheritance information leaflet
X-linked Inheritance information leaflet
All of our cells contain ‘power stations’ called mitochondria. Mitochondria contain a small number of genes. When sperm and egg fertilise to create an embryo, all of the mitochondria in the embryo are inherited from the mother's egg.
If there is an alteration in one of the genes in the mitochondria of a woman, she can pass this on to her child. If there is an alteration in a man’s mitochondrial genes, he will not pass this on.
This describes the cause of medical conditions which are due to a combination of genetic alterations and factors in our environment. In the rarer single gene disorders (inherited as dominant, recessive or X-linked) an alteration in one gene can cause a condition. Other more common conditions may be caused by alterations in several genes, each of which has only a small effect.
For example, our risk of some types of cancer may be increased if we have a certain combination of these genetic alterations. Our risk could then be further increased by factors in our lifestyle, such as whether we smoke or not.
We are only just beginning to understand this kind of inheritance, and no genetic testing is available at present.