Pre-implantation genetic diagnosis (PGD) is the process used in reproductive science to profile the genetic makeup of embryos before they are selected and implanted as part of the in vitro fertilization (IVF) process.
Most often, couples carrying – or who are at a higher risk of being the carriers of – a genetic disorder use PGD so as not to pass on a specific genetic abnormality to their offspring. Cystic fibrosis, sickle-cell disease, Huntington’s disease, Duchenne muscular dystrophy, fragile X syndrome and a host of other life-threatening conditions can be detected through PGD.
PGD allows us to avoid devastation from these diseases, as we can select embryos that will have the best chance of avoiding genetically inherited abnormalities.
As a reproductive endocrinologist, it’s my obligation to provide information and guidance to my patients considering the PGD embryo biopsy. Ultimately, each patient must decide whether to use genetic testing based on his/her unique social, religious and environmental circumstances.
Great strides in the field of genetics have been made since PGD’s beginnings in 1989. While we are able avoid some diseases with the use of PGD, less is known about how to control diseases that may be linked both by genetics and environmental factors.
Understanding your genes
More than 10 years have passed since the Human Genome Project successfully mapped the properties of approximately 25,000 genes, which comprises a majority of all human genetic information. This feat has equipped scientists with a “blueprint” to better understand the physical and functional properties of single genes.
Defining the properties of human genes was an important first step of understanding biological codes and how they dictate development from an embryo to a human.
The major challenge, now, is to discover the sources of what exactly makes that coding go awry. Scientists are looking at what triggers a gene – which may exist as seemingly normal for many years – to malfunction and manifest in the body as cancer, for example.
A common misconception about genes is that they dictate who and what you are: that’s only part of the story. Genes only tell you what your capacity for being is. In actuality, it’s the environment – and influencers within the environment – that humans are exposed to that activate or turn off genes.
It may not necessarily be the case that you have an abnormal gene by inheritance, rather it’s that you have a gene that is inadvertently shut off or turned on at a point in time that triggers disease.
While some people are genetically predisposed to illnesses like cancer, environmental and behavioral factors play a much more significant role in the presence of a disease in the body.
Consider the environments that we live in
While PGD has given scientists the ability to screen for genetic abnormalities – and select embryos that will not carry a genetic mutation – we know very little as to the environmental conditions that make genes mutate into a disease such as breast cancer.
Research has shown that smoking can cause lung cancer and heart disease can be the result poor diet and lack of exercise. There are very clear behavioral modifications that individuals can control that will help them prevent the development of these diseases, entirely separate from their genetic profiles.
We know that the environments that we live in greatly alter our personal health, but will science help us to better understand the necessary steps to live a healthy, fulfilling life? Time will tell. For now, PGD has a proven value in alleviating human suffering that can be highly beneficial to appropriate candidates.