a cancer cell

In 2000, researchers managed to decode the genome of a human being.  This was heralded as a great breakthrough, and the hope was that genetically based treatments would revolutionize health.

10 years later, very few treatments or changes in medicine have arisen from this.

Why?  Simple.  Sheer complexity, even more so than originally suspected.

There are some uses, of course.  Response to Plavix, a popular blood thinner, can be predicted in part by genetic profiling.  Additionally, cancer treatments Tarceva and Iressa are also predictable to some degree by genetics.

Even then, the limitations are many.  Genetic profiling can predict with 80% accuracy whether someone will respond to a treatment of interferon for hepatitis C – but this doesn’t matter.  The test is expensive and time consuming, and since there are no other options, it won’t have an impact on the course of therapy.

Disease transmission is highly complex

The most simple case of disease heritance is single gene transmission.  There, one gene alone is associated with the disease.  You can have one or two copies of it (from Mom and Dad) and this in theory alone predicts disease likelihood.

Even there, having the disease gene doesn’t always cause disease.  You can have all the genes for a disease, yet be in perfect health.  This is called penetrance: or what percentage of the time that a gene is actually going to cause problems.

That is just one of many exceptionally complex factors that influence disease expression.

Then there is the epigenome.  This is a system of genetic control that is regulated by the environment.  It is a recent discovery – we used to believe that genetics were solely herited, and not influenced by the world.  That is no longer believed true.

The world and environment changes our genetic system as we live.

An extreme example of epigenetics is fetal alcohol syndrome.  There, the baby’s environment causes changes that are expressed in the genome.

Hope for genetically based therapies arose in 2005 when a specific type of research found answers.  There, the method of research called ‘genome wide association’ looked at many people’s genetic info who had the same disease, age related macular degeneration.

It looked for genome wide features associated with it.  And it struck gold, finding genetic info that was a relative risk factor of 4.6, or 4 times as likely to have it than without.

Yet since then there has been little progress.

Making things exceptionally complex, most conditions are controlled by many different genes.

20 or more genes can contribute to a condition.  Each of these genes can play different roles.  And environment can greatly alter how each gene works.

The worst part?  Even in the cases where genetics is useful in providing risk assessment for some diseases, it often is not too different than what you’d figure out anyway.

So a 50 year old man might have a 10% chance of a certain heart condition by population studies.  Genetic research might find the same number, which is of little use.

In the end, the breakthroughs due to genetic research will come and they will be dramatic.  They are likely to be different in nature and timing than the popular media may present.



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