Britain’s NHS recently announced plans to offer DNA tests in exchange for patients consenting to share their DNA data. This marks one of the world’s biggest initiatives in genomic data gathering. As a result, experts could develop new treatments for a range of genetic diseases.
But what can DNA sequencing really tell you, and what are its limitations? We take a look at the facts.
The NHS began the initiative to gain more genetic data on the general population.
The new initiative is being set up to create genetic datasets from the general population rather than targeting specific diseases for which diagnostic testing is already available. The NHS is seeking out healthy individuals to become genomic volunteers. Candidates will provide DNA by blood sample. Their unique DNA profile will be added to a genomic database.
As the UK Health Secretary Matt Hancock points out, such data is of huge value scientifically. Every genome sequenced brings us one step closer to developing potentially life-saving treatments for a range of genetic conditions.
By analyzing blood samples, researchers can test for gene mutations. These anomalies in DNA sequences are what to make them different from those found in normal, healthy individuals.
Not all gene mutations are bad.
Gene mutations are quite common. Scientists estimate that the average healthy person carries around 60. Gene mutations dictate the way we look and how our bodies function. However, they can sometimes make us more (or less) susceptible to disease.
For example, scientists discovered that the gene mutation that causes sickle cell anemia also bestows malaria resistance. Studies by Portugal’s Gulbenkian Institute of Science revealed that those who carry sickle cell disease are less likely to contract malaria. Researchers have observed for some time a much higher incidence of sickle cell disease in malaria-affected regions.
Sickle cell disease is a recessive disorder, meaning that generally both parents must carry the same gene mutation in order for their child to inherit the condition. Recessive diseases tend to pass silently through the generations, only causing symptoms in the children of two carriers. It is thought that sickle cell disease effectively “piggybacks” on the positive trait conferred by malaria resistance in evolutionary terms.
We each have around 24,000 genes.
Genes are contained within our genome, which is found in virtually every cell of the body. The human genome is a complicated set of genetic instructions. It dictates our physical characteristics and the way in which our bodies function, passing on data vital to complicated physiological processes, such as how to synthesize proteins.
Approximately 99 percent of human DNA is non-protein coding. There is extensive research regarding protein coding DNA. Scientists are only just beginning to realize the significance of non-coding DNA, which until relatively recently was considered “junk DNA” of little scientific value. Researchers now believe that non-protein coding DNA may play a significant role in regulating protein coding DNA.
Some gene mutations cause disease.
Most gene mutations have a neutral effect, and can even bestow positive traits. However, some gene mutations can make us more susceptible to disease.
Scientists have identified over 4,000 diseases caused by gene mutations. Here, genetic anomalies prevent genes from functioning properly, directly resulting in a genetic condition. Common genetic conditions include: thalassemia, sickle cell disease, hemophilia, cystic fibrosis, Tay-Sachs disease, fragile X syndrome, and Huntington’s disease.
Researchers have also detected certain genetic markers suggesting a predisposition to certain diseases, such as: cancer, diabetes, cardiovascular disease, and asthma.
Gene sequencing can help identify risk.
It is important to understand that in detecting genetic markers for diseases like cancer and diabetes, gene sequencing can reveal a predisposition to those diseases. However, it cannot provide definitive answers as to whether or not a person will develop that disease in his or her lifetime.
Most common illnesses are not caused by a single-point gene mutation, but a series of anomalies, making them harder to predict. An individual’s lifestyle as well as environmental factors can also contribute to the risk of developing diseases like cancer. Variables such as diet and exposure to carcinogens have been shown to have a strong influence on disease risk.
Because of this, individuals who receive “low risk” results could still go on to develop the disease. The key to improving risk prediction is collecting more comprehensive datasets.
DNA sequencing has great potential for cancer care.
DNA sequencing is not only used to predict cancer risk, but also to treat the disease. Rather than concentrating on the DNA of the individual, medical practitioner’s sequence the DNA of the tumor itself. They then compare and contrast it with healthy cells from the patient.
This can help specialists identify the most appropriate treatment, and predict how the tumor will react based on its unique genetic alterations. This approach takes a lot of the guesswork out of cancer treatment, marking a shift away from a “one size fits all” approach, towards precision medicine and personalized medical care.