We all know that children often look like their parents, and that brothers and sisters often look like each other as well. This is due to biological inheritance, where information is passed through the generations from parents to children. The source of this hereditary information is a biological device called a gene. A child is a 50/50 combination of the genes of both its parents, who were in turn a 50/50 combination of their parents. This means that genetically each of us is a unique, individual blend of all our ancestors.

Variations in genes are quite normal and produce differences in height, hair and eye colour, and other characteristics, even among those who are closely related. These variations are part of the ordinary diversity of the human race. However, if a gene is faulty it may result in the failure of the body's cells to carry out their usual function. This may be either the direct cause of a disease or disability in a person, or increase their susceptibility to a particular condition.

In genetic diseases, the disease may appear in the child if a faulty gene is passed on from parents to child. This may occur whether either parent had signs of the disease or not.

NZORD recommends the following sources of material to get a good understanding of how these factors interact to cause the disease or disability that has appeared, or may appear, in you or your child:

The New South Wales Genetics Education Programme has a series of Fact Sheets on a range of genetic topics including the basic biology, genetic causes of disease, and patterns of genetic inheritance. The same facts sheets menu is accessed through the "students", "professionals" or "patients and families" links on the site. They are well written and should be understandable for those with no prior knowledge of the subject.

Learn.Genetics sponsored by the University of Utah provides excellent educational resources on its website, including resources designed for children as well as more advanced readers.

The Genetic Alliance UK provides brief guides to genetic disease and inheritance on its site. The guides are written for those with little prior knowledge of biology and genetics and is a good introduction to the subject for beginners.

The Dolan DNA Learning Centre, hosted by the Cold Spring Harbor Laboratory, provides DNA From the Beginning, an animated tutorial on the basics of DNA, genes and genetic inheritance. Suitable for students, lay-readers and professionals who need to brush up on their knowledge in this area. Its content ranges from the basics to more advanced concepts. Some advanced programmes will be required to cope with the audio, image and animation features in the tutorial. The Dolan site also has useful information on the history of eugenics with important lessons we must never forget.

Science Learning and Biotechnology Learning Hub: These two websites provide easy to access information about science, generally and biotechnology, specifically. They are designed for use by school-age children, so the information included is not technical but provides an excellent starting point for those new to science and biotechnology.

More advanced reading:

An Introduction to Genetic Analysis is an online textbook suitable for students and professionals who want to revise or extend their knowledge of genetic issues. The book is accessed through the Bookshelf page of PubMed.