Genomics 101: Genetics vs genomics, what's the difference?

In this series, ‘Genomics 101’, we go back to basics and explore some of the most important topics in genomics. In this blog, we explain the terms genetics and genomics, and how they are different from each other.

First things first, what is genetics?

Genetics is the study of genes and how we inherit characteristics from our parents.

For example, genetics might tell us how a physical trait, behavioural trait, or health condition is passed down from parent to child.

So then, what is a gene?

To understand the meaning of the word gene, we first have to understand DNA.

DNA is a molecule found in all living things. It carries the information we need to survive, function and grow, like an instruction manual for our body.

The cells in our body can read these instructions, almost like reading a book, and produce all the different proteins we need to survive.

A gene is a section of DNA that contains one specific instruction.

For example, humans have a gene that determines our eye colour. Some people have a gene that leads to brown eyes, and others have a gene that leads to blue eyes. 

How many genes do we have?

Scientists aren’t completely certain on the exact number of genes we have, although estimates suggest around 20,000 pairs.

One gene from each pair comes from our mother, and the other one comes from our father. 

So then, what is genomics?

The genome is the complete end-to-end sequence of DNA present in each person. 

It is made up of all 20,000 of our genes (plus some other sections in between) to encode all the vital information we need to survive.

Put simply, genomics is the study of this genome.

How is genetics different from genomics?

Genetics and genomics both study DNA, however, genetics is the study of one or a few genes, whereas genomics looks at the entire genome.

This means that in genetic testing, researchers will analyse a single gene or specific group of genes, sometimes known as gene panels.

However, in genomic testing, scientists analyse many different sections of the genome all at once, from one single test.

When would genetic tests be used instead of genomic tests?

Good question! There are many different cases where genetic tests would be used instead of genomic tests.

For example, there are several specific genes that are known to be linked to breast and ovarian cancer. 

If a family has a strong history of these cancers, they may have a genetic test to see if any particular gene is causing this cancer. This in turn help to guide the family's care.

So, when would you use genomic testing?

There are lots of cases when genomic testing might be chosen over genetic. For example, if a person has a rare genetic condition, and genetic tests so far have not been able to reveal the cause.

In cases like this, tests such as whole genome sequencing can give us a broad overview of the person’s DNA, letting us look across lots of different genes all at once, to try and find out more about what might be causing the person’s condition. 

A key example of large-scale genomic testing is the 100,000 Genomes Project. This landmark initiative sequenced the genomes of over 85,000 participants affected by rare conditions or cancer.

Carried out by Genomics England in close partnership with the NHS, the project aimed to find answers for participants, and later led to whole genome sequencing becoming part of routine care.

Though sequencing for the project was completed in 2018, approved researchers are still looking through the DNA sequences every day to try and find answers for participants and their families.

What happens if I mix genetics and genomics up?

Though genetics and genomics mean slightly different things, some people might use them interchangeably, or say genetics when they mean genomics, and vice versa.

Though this might get confusing, try not to worry about accidentally saying the wrong thing. Both genetics and genomics involve studying our DNA to better understand how it can affect our health.