DNA genetic testing kits.

The rapid development of DNA sequencing technologies which deliver fast, accurate and affordable DNA sequence information has made genetic testing much more accessible for individuals than ever thought possible.
This information sheet seeks to summarise what you as individuals can learn from commercially-available DNA kits. We also summarise the ongoing CHRC study analysing populations of family trios using whole genome sequence technology.

DNA genetic test kits

Commercially available DNA test kits, such as 23andme Inc., use a DNA sample from a customer to determine, in part, their genetic code (DNA sequence) and look for various DNA markers. These markers are specific to the information the DNA genetic test is testing for. For example, there are different markers for ancestral origin and for particular medical conditions. Table 1 details some of the commercially available tests and what they are testing for.

Table 1: Commercially-available DNA test kits

¹E.g. BRCA1/BRCA2, Celiac Disease, Glucose-6-Phosphate Dehydrogenase (G6PD) Deficiency, MUTYH-Associated Polyposis, Late-Onset Alzheimer’s Disease, Parkinson’s Disease.
²E.g. Glioma, Osteosarcoma, Type1/2 Diabetes, Schizophrenia, Multiple Sclerosis and Coronary Heart Disease.
³Genomic Data is the raw data from sequencing an individual’s genome completely or partially. Genomic Data received from DNA tests, can be utilised by clinicians in diagnosis of patients who are at higher risk of genetic errors resulting in diseases.

Where can I find DNA test kits? 

DNA tests are commercially available through online websites (see Table 1). Companies will send out packs with an explanation for providing a sample. Your DNA is then isolated from the sample you have sent in (cheek swab or saliva/spit sample) and elements of the DNA sequence determined. The results are analysed and a report is sent back to you.

What do they test for?

DNA test kit services can provide information on your individual health and/or ancestry. They can inform on health risks for developing certain conditions and the potential for heritable traits to be passed on to your children.
Most DNA test kit results will provide a risk estimate for developing a condition. There is no certainty that an identified health issue will happen. A risk estimate provides information on the likelihood you will get a health condition compared to the average population. For example, if you have an increase in 3% risk of a specified health effect, and the current population has a 2% risk, your personal risk is 5%. Which means you have a 1 in 20 chance of developing the condition, but you are far more likely to be in the 95% of people (who have the same risk) who do not get this health condition. The information from these tests do not account for other non-inherited factors, such as smoking or unhealthy eating, which can also change your risk of getting certain health conditions.

What are the risks in using a commercially available DNA test kit?

The information provided to you may be mis-leading and could potentially cause needless worry. For this reason, genetic testing which seeks to understand heritable risks is only advisable when accompanied by a genetic counsellor.
The information you receive may be meaningless with respect to particular questions of interest. For instance, the results you receive will only relate to the DNA you inherited and your health risks for specified conditions. The results will not provide information on the cause of any mutations.

DNA sequencing for the CHRC Genetic and Cytogenetic Study.

How does it differ to DNA test kits?

We are using Next Generation Sequencing techniques to determine the DNA sequence of the entire genome for each member of a family trio (father, mother, biological child). We are doing this for 30 nuclear test veteran families (test population) and 30 veteran families (control population) with no known participation at test sites.
We are then comparing the genomes from the two different populations to detect any differences or ‘variants’ between them. These differences might be single nucleotide variants (SNVs), variants that are short insertions or deletions (indels), or larger structural DNA variants (SVs), such as gene copy number variants (CNVs).

De novo (newly arising) DNA mutations

New DNA mutations contribute to the natural process of DNA variation and arise as a result of DNA damage. DNA damage occurs naturally throughout life and is usually corrected very efficiently by DNA repair processes. However, when damaged DNA is not correctly repaired then errors called mutations accumulate within the genome. An excess of DNA mutations can occur when a cell’s response to DNA damage is compromised or overworked, and when a cell is exposed to chemical mutagens or ionising radiation.
A new DNA mutation that arises in a germ cell (egg or sperm) of one of the parents and which is then transmitted to the child or children, or in a fertilized egg cell itself, is called a de novo or newly arising mutation (DNM). Newly arising mutations may or may not be associated with a particular health condition in the child.
In our study we are looking for DNMs that may have arisen in the germline of British nuclear test veterans as a consequence of veterans participating at nuclear bomb test sites. DNMs are DNA variants which are present in the child but not in either of the parents’ own (somatic cell) genomes.
Although DNMs induced by ionising radiation may themselves be largely indistinguishable from naturally occurring DNMs, we can look for deviations in the expected number and pattern of DNMs because we are comparing our data to the control family population.
Previous work has shown that DNMs arising from exposure to radiation may include more clustered SNVs and more CNVs, and that more DNA mutations may also occur at highly mutable repeat regions compared to the general population.

Will this study answer health questions?

Our study has been designed to seek out evidence for genetic damage caused by historical participation at test sites. Having a higher level of genetic damage is thought to increase the risk of developing some medical conditions, but this outcome is fortunately not an absolute.
If we were to find evidence of radiation-related genetic damage in the population of NTVs or in their families, we could not conclude that this was the cause of the range of reported ill health issues. Instead, this finding would direct research where the meaning for health may be explored in much greater detail.

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