Tutorial 2: What are genetic disorders?

Tutorial 2 categorizes the types of genetic disorders and looks at how genes affect our lives.

Penny

Tutorial 2: What are genetic disorders?

In the 50 odd years since since Watson, Crick, Franklin and Wilkins first discovered the structure of DNA in 1953, knowledge of how genes play a role in health, disease and disability has rapidly grown.  These days we are bombarded with stories about genetics in the news and not a day goes by without an announcement describing a new genetic test or breakthrough.

There are two categories of genetic disorder – Single Gene Disorders and Complex (multifactoral) Diseases.

1. Single Gene Disorders

Single Gene Disorders are where there is one faulty gene causing disease regardless of the environment.  There are over 10,000 different single gene disorders, together these conditions can cause more suffering for up to 5% of the population.

Examples include cystic fibrosis (www.cff.org), sickle cell anemia (www.sicklecelldisease.org), thalassemia (www.thalassemia.org), Duchenne muscular dystrophy (www.muscular-dystrophy.org), hemophila A (www.hemophilia.org), Huntingdon’s disease (www.hdsa.org), neurofibramatosis (www.ctf.org) .

These single gene mutations are uncommon to very rare but the effect of the mutation is usually quite marked, regardless of other influences.  There are genetic tests available for affected families, provided through specialist genetic services.

2. Complex (multifactorial) disease

Complex multifactorial genetic disorders are far more common and affect all of us in some way.  In these conditions, changes or mutations in one or more genes don’t inevitably lead to disease but do predispose us to the effects of other, environmental factors, increasing our vulnerbaility to common chronic conditions.

Examples include heart disease, high blood pressure, Alzheimer’s disease, arthritis, diabetes, cancer, obesity, asthma, eczema.

Inheritance patterns are poorly understood.  There are an increasing number of disease risk assessment tests becoming available on the market which look at a group of single letter mutations or ’spelling mistakes’ which when combined increases an individual’s risk of developing a certain disease.  The challenge presenting the medical and scientific communities is to understand the role and interaction of these mutations/spelling mistakes and to understand how far genetic status may affect lifestyle choices.