What is genomics?
Genomics is the study of the whole set of a person’s DNA called the genome. Our DNA makes us who we are. DNA has codes for genes that gives us traits such as our hair colour, eye colour, and height. We might also have an increased chance to develop certain diseases because of our genes.
So, genomics can be a powerful tool to detect risk of disease. This can help you manage and take action to improve your health and potentially prevent disease. Here I explain how genomics works.
What is the genome?
All of the cells in your body have DNA, which is made up of bases. There are four bases, represented as letters: A,T, C, and G. These join in pairs; A always pairs with T, and C always with G. Your DNA has billions of these bases. These bases form sequences that make up genes that code for proteins, like the letters of the alphabet that form words.
Proteins are the building blocks of our bodies. Genes gives us traits such as our height and eye colour. But genes only make up around 2 percent of your genome.
A lot of DNA sequences don’t code for genes (non-coding regions). Non-coding regions used to be called “junk DNA” because scientists once didn’t know what they did. But there’s now evidence that non-coding DNA plays important roles in the body.
All of the DNA in a cell or organism is called a genome. And genomics is the field of study that looks at the genome, both the coding and non-coding regions.
Between people, our genomes are around 99.9 percent identical. But in that 0.1 percent are differences that make us unique. These differences in the genome are called variants.
Some variants are harmless, while other variants might make us more likely to develop disease. By studying the genome, we can find out more about how genes work, including how they may increase risk of disease.
By knowing more about how our genome affects our health we can manage or prevent disease.
What genomic testing is there?
Genomic testing can be done in different ways. Below are some types of genomic testing.
Newborn screening
In the UK, babies are screened to find out if they have some genetic conditions such as sickle cell disease. This is done using a blood sample from a heel prick test.
Diagnostic testing
If you have symptoms your doctor might recommend a genetic test, if they think there is a genetic cause. This may help to confirm if you have a genetic condition.
Predictive testing
You can have your genome tested if you don’t have any symptoms. This could find variants that increases your risk of developing a certain disease in the future. Testing can be done for a single gene known to cause a disease, such as for breast cancer or Huntington’s disease. It can also be done for multiple genes, for more complex diseases such as heart disease.
Carrier testing
We have two copies of each gene, one from each of our parents. Sometimes one of the two genes does not function properly. Thankfully, the other normal gene can make up for the faulty one, so overall the person doesn’t develop the disease. In this case, you are said to be a carrier of the condition.
Carrier testing can be helpful to see if you carry a specific gene for a disease that might be passed on to your child. If your partner is also a carrier for the same condition, there is a chance that your child will inherit both disease-causing variants from you and your partner. This can lead to them developing the disease.
What can genomics tell us about our health?
Some diseases are caused by lifestyle factors such as smoking and diet, while some can be because of genetics. Many diseases are multifactorial or complex, which means both genetics and the environment are involved.
By analysing your genome, you can find out if you have a mutated gene or genes that put you at risk of developing certain diseases.
You can then work with a healthcare professional to take action to minimise your risk. For example, if you are tested and have a gene variant for breast cancer, you could attend mammograms regularly to monitor your risk.
Genomic testing can also help if you’re planning to have a family. If you and your partner are carriers of a gene that causes the same disease, your child might be affected by the disease. Knowing you’re a carrier can help to potentially diagnose the disease in your child early and deliver early treatment.
It can also help you make family planning decisions. One option could be to undergo IVF with embryo screening. This involves screening embryos and selecting only embryos that don’t have the disease-causing gene.
What is genetic counselling?
Finding out about your genes and risk of disease can help to detect disease early, before you even get symptoms. But there’s a lot to consider when getting this information.
So, if you do undergo genomic testing, it’s best to speak to a genetic counsellor. This is a type of counsellor who helps you understand what your genomic testing results mean for you and your family.
Genomics is still a growing field and there’s still a lot more to be discovered. But there’s also a lot of potential for genomics in improving health. If you want to know more, you might find the below websites helpful:
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Sources Sources
- Genomics toolkit. RCGP Learning. elearning.rcgp.org.uk, accessed January 2025
- Understanding genomics. Genomics England. genomicsengland.co.uk, accessed January 2025
- Genomics 101: What is non-coding DNA? Genomics England. genomicsengland.co.uk, published September 2024
- Newborn blood spot screening: programme overview. NHS England. gov.uk, last updated July 2024
- Genetic services and testing. Genetic Alliance UK. geneticalliance.org.uk, accessed February 2025
- Genomics Beyond Health. Government Office for Science. gov.uk, published January 2022
- Glossary and further reading. Genetic Alliance UK. geneticalliance.org.uk, accessed February 2025
- Ormondroyd E, Border P, Hayward J, et al. Genomic health data generation in the UK: a 360 view. Eur J Hum Genet. 2022 Jul;30(7):782-789. doi: 10.1038/s41431-021-00976-w
- Embryo testing and treatments for disease. Human Fertilisation and Embryology. hfea.gov.uk, published September 2024
- Genetic counselling - a guide for GPs. Patient. patient.info, last updated August 2023
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