Genetics or Genomics?


You say genomics, I say geneticsAt TGMI meetings we often have energetic discussions about the best language and terminology to use. One of our earliest language debates was on whether to use ‘genetic’ or ‘genomic’ medicine in our name.

 

What does ‘genetic’ mean?

Definitions of ‘genetic’ are largely consistent, and the word is generally used in the same way in scientific and everyday language.

Wikipedia defines genetics as ‘the study of genes, genetic variation and heredity in living organisms’. So the word ‘genetic’ is used to describe inheritance and/or that something is related to genes.

For example, the sentence “cystic fibrosis is a genetic condition” can be used as a substitute for “cystic fibrosis is an inherited condition” and for “cystic fibrosis is due to mutations in the CFTR gene”.

One might reasonably ask how often is this dual use a cause of confusion in medicine? Overall, relatively infrequently. Largely because many genetic conditions are both due to gene mutations and are also heritable, so both definitions are fulfilled.

Use of the word ‘genetic’ is confusing in cancer

The word ‘genetic’ is used to describe inheritance and/or that something is related to genes.

Cancer is one important area where use of the word ‘genetic’ regularly leads to misunderstanding. Cancer scientists often say that “cancer is a genetic disease”. Indeed, searching for this sentence in google today gave 77,400 hits! The phrase is used to convey that all cancers have gene abnormalities in the cancer tissue (called ‘somatic’ changes). So the definition of genetic as something related to genes is satisfied.
However, somatic mutations are not present in non-cancer cells in the body, they were not inherited, they cannot be passed on to children. Thus the second meaning of genetic is not fulfilled in this context.

In fact, only about 3-5% of all cancers are due to inherited gene mutations, though the proportion varies by cancer type. Many people, including many clinicians and scientists, are under the misconception that it is much higher, in part because of how the word genetic is used in cancer research.

 

What does ‘genomic’ mean?

Definitions of ‘genomic’ and ‘genomics’ are more varied and inconsistent. Both within science and between scientists and non-scientists.

Overall, outside science, many people use genetics and genomics interchangeably, in situations where they would previously only have used genetics. This is particularly true in healthcare where genetic medicine and genomic medicine are often used equivalently.

I am frequently asked what genomics is. Many non-scientists, including health professionals, remain unclear about it, though people inside the field are sometimes incredulous to hear this! By contrast, I cannot remember the last time anyone asked me to explain what genetics is.

 

The word ‘genomics’ is used in different ways in science

Many people, including many in healthcare, are unclear what ‘genomics’ is.

In academia the word ‘genomics’ can be used in several ways. It is often used to describe the area of science engaged in gaining knowledge about the genome. For example, the wikipedia definition is: “Genomics can be considered a discipline in genetics. It applies recombinant DNA, DNA sequencing methods, and bioinformatics to sequence, assemble, and analyze the function and structure of genomes.”

More recently, the word ‘genomics’ has begun to be used in a broad sense to not only refer to DNA based features of the genome, but also to encompass other aspects such as the transcriptome (the messenger RNA expressed from the genes). The term ‘genetics’ is not used in this way. Additionally, ‘genomic’ is seldom used, on its own, to imply that a condition is inherited.

“Cancer is a genomic disease” is not used very often. There were only 3,150 hits for it on Google today! This is rather unfortunate. It is more appropriate than “cancer is a genetic disease”, because many cancer driving abnormalities alter the genome, but not specific genes. Moreover, it is much less likely to be interpreted as implying that cancer is an inherited disease.

 

Why did TGMI choose genetic?

TGMI stands for the Transforming Genetic Medicine Initiative. Using genetic rather than genomic was against the tide. Most similar initiatives have chosen genomic. So why did we choose genetic?

  • The term ‘genetic’ has a clear definition that is used consistently by the public and academia. TGMI is targeted at a broad audience, so this is important to us.
  • TGMI is focused on our genes, which encompass only 1-2% of the genome. Using ‘genetic’ makes this more explicit.
  • TGMI is focused on DNA sequence variation in genes, not changes in gene expression.
  • TGMI is focused on defining which of our 20,000 genes can cause disease. It is these types of conditions that the majority of people think the term ‘genetic disease’ refers to. We are not addressing common variants in the genome that have small impacts on disease risk, or somatic genetic changes that drive cancer.

 

Does it matter?

On many levels it doesn’t matter much which word one uses. And these semantic discussions can seem trivial given the huge work that needs to be done to make genetic/genomic medicine work.

But consistent use of universally understood language is a powerful, effective dissemination aid. It is particularly important when trying to move something from a small-scale endeavour performed by specialised practitioners in rare individuals to a large-scale enterprise, performed through many, diverse routes and of relevance to millions of people. So we should at least pay attention.

Of course, one of the benefits of using acronyms is that people quickly forget what the underlying letters stand for. So if it becomes appropriate to ‘upscale’ our ‘G’ to stand for ‘genomic’, as it might in this fast-moving field, probably few people will notice!

 


5 thoughts on “Genetics or Genomics?

  • Ron Zimmern

    Dear Nazneen

    Whether I agree or not with your arguments will depend on what you consider to be the scope of TGMI’s work.

    If it is primarily confined to inherited (or heritable) disorders then the use of the word ‘genetics’ is entirely justified. The word ‘genetics’ was first coined by William Bateson in 1905 to describe the study of inheritance and the science of variation. Clinical geneticists are thus experts on inherited or heritable disease in the same way that cardiologists are experts on heart disease.

    By contrast, the word ‘genomics’ refers to the ‘genome’ of living organisms and may be used in all cases where the relationship between genes (or non gene elements) of the human genome and disease (or physiological traits) are being studied. ‘Genomics’ need not have any connotation of inheritance or of inherited disease.

    But I suspect TGMI’s interests may not be confined to inherited or heritable disorders. You state explicitly that “TGMI is focused on defining which of our 20,000 genes can cause disease”. The relationship between those genes and the causation of disease is generically the subject matter of genomics and NOT genetics. Because of Bateson’s original definition ‘genetics’ can, in my view, legitimately be used to discuss the relationship between gene and disease if applied to inherited or heritable disorders. Alternatively it may also be used to describe the study of transmission of genes across generations in other disorders. But IT SHOULD NOT BE USED when dealing with the relationship between gene and disease if the disease is not inherited or heritable. Therein lies the confusion when describing cancer as a genetic disease.

    I very much understand that those from a clinical genetics background might prefer to use the word ‘genetics’ in a generic fashion, but I would argue that this is not correct and I suspect that other scientists and physicians would probably agree with me. You may be interested to know that I had the same email conversation with John Burn when he changed the name of the BSHG to the British Society of Genetic Medicine.

    Best wishes

    Ron

  • Nazneen Rahman Post author

    Dear Ron
    Thanks so much for taking the time to post this comment, and for adding the historical perspective.
    You will be pleased to hear that the TGMI is primarily focusing on clarifying which of our genes can cause inherited (or heritable) disorders, in line with Bateson’s original definition. I agree that it is appropriate to limit genetic to this usage.

  • John Burn

    Thanks Naz and Ron for a clear explanation of what I suppose could be called the G spot! One correction Ron is that the decision to change BSHG to BSGM was a democratic decision. I think Naz is right to stick to the pragmatic high ground of a focus on the genetic changes that are useful at the clinical interface. I also agree that the meaning of “Genomics” has migrated to be descriptive of all the “Omics” which is why I have spoken of its rise and fall-once Genomic knowledge becomes ubiquitous in medical practice, Genomic Medicine will simply become “Medicine”.

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