Ancestry and disease: what have we inherited?

Studying our genes is becoming a big business in health care. New gene discoveries make great news. Every week we hear about another gene that can identify our susceptibility to a particular disease or be modified to produce a cure. With over 3.0 billion human genes that is no mean feat.  Unfortunately, cure is not that simple and very few genetic breakthroughs result in effective treatments. Genetic discovery is a long way from becoming an effective treatment.

Exploring ancestry can help us understand which social and environmental factors precipitate diseases in some people and not in others.

Genetically simple diseases, like cystic fibrosis that is caused by an alteration of a single gene, gave us hope that these discoveries would lead to a whole new way of effectively tackling disease. However, these single gene diseases are rare.

Whilst researchers have made tremendous progress in understanding the genetic basis of rare, single gene diseases, the challenges become enormous once the basis of a disease extends beyond a single gene. Determining exactly which genes found in any patient actually contribute to their disease is not simple. With improved research techniques, even diseases that were thought to be caused by a single gene may now be caused by changes in a number of different genes. Complex diseases such as cancer, autism, diabetes, obesity, and some psychiatric conditions such as depression are known to have hereditary components. The converse is also true. Some genes which were implicated in diseases are now found to be harmless.

The history of how we got these genes has been of interest to geneticists for many years. Genealogical graphs are frequently used to study how a genetic disease reveals itself in families.

Both geneticists and gene researchers work from the current data that is provided usually because someone is sick. The growing interest from amateurs in ancestry can provide a new route for looking at the impact of genetic heritage.

Researching ancestry can go beyond the medical focus on genes and how they cause diseases. Understanding the history of families can help us understand which social and environmental factors precipitate diseases in some people and not in others.

Beyond genes and the study of them, there remain many more pieces to the disease puzzle waiting to be described.  Other components of our history live in our cells but not in our genes. They are becoming more important and may influence the way the building blocks of our cells join together in the development of diseases such as diabetes, epilepsy, Alzheimer’s and Parkinson’s diseases.

Despite all these challenges to further understanding how our genetic heritage affects our health, we should, however, count ourselves lucky that relatively speaking, that the human genome is quite small.  The largest genome that has been identified belongs to the Paris japonica flower. It is 50 times larger than the human genome.

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