Old black and white photo of postmen on bicycles leaving from Christchurch, NZ, Central Post Office c.1900

July 4, 2024, by Brigitte Nerlich

Blueprints, postmen and a bit of metaphor archaeology

At the end of June, the NHS announced a new gene therapy for haemophilia B. Gene therapy replaces a faulty gene or adds a new gene to correct a mutation (genetic fault).

People with haemophilia B lack the blood clotting protein factor IX and can bleed severely from even a slight injury. Some therefore need frequent injections of this missing protein. The drug used in the new gene therapy is Hemgenix (etranacogene dezaparvovec) and is given by a one-off infusion which should enable the body to produce factor IX itself and prevent and control bleeding.

The announcement didn’t cause huge waves in the news, but the BBC’s health and science correspondent James Gallagher picked it up and did some interesting science communication.

Conventional and novel metaphors in science communication

Gallagher follows the story of one haemophilia patient, Elliott Collins, and tells us that “Elliot was born with a mutation in his DNA – his genetic code – that meant his body’s instructions for making factor IX were faulty.”

Here we have the classic gene/DNA metaphor, of DNA as a code, but not any code, a code, that gives the body instructions. Normally, in text books and on websites, this metaphor is expressed as, for example: ‘the genetic code refers to the instructions contained in a gene/DNA that tell a cell how to make a specific protein’. It is a ubiquitous and conventional metaphor (for good or for ill).

But Gallagher goes beyond the old code metaphor and introduces a new one (a metaphor he had first used, it seems, when talking about Covid vaccines). This metaphor is, however, as we shall see, rooted in an older, more hidden, one. He writes:

“So doctors gave him engineered viruses that contained copies of the fully functional factor IX instructions. The viruses act like a fleet of microscopic postmen, delivering those blueprints to the liver. The organ is then able to manufacture the clotting protein.”

Engineered viruses sound a bit dangerous. But these viruses are not like normal ones; they are what the scientific literature calls ‘viral vectors’, that is, tools designed to deliver genetic material into cells. Gallagher portrays them as little postmen, indeed a whole fleet of them delivering post to the cell (my husband imagined them sitting in little boats). The post they deliver are ‘copies’ of ‘instructions’ for the cell about how to do something.

These instructions arrive in the form of ‘blueprints’ which allow the cell to become a manufacturing or construction centre. One can just imagine the cell opening a letter and reading out the instructions to its manufacturing staff, if you like (although blueprints are not really instructions, as some expert architect has to interpret the drawings, but never mind). Like the code metaphor, the blueprint metaphor is another very old and very conventional metaphor used in the context of talking about DNA.

I’ll now dig a bit deeper into the history of the blueprint metaphor before getting to the postmen metaphor. As you’ll see, metaphors are like the tips of icebergs revealing but also hiding lots of accumulated cultural and scientific knowledge.


Let’s first look at the blueprint metaphor. It’s nowadays very contested but has a long history. The metaphor basically implies that just like architectural plans are blueprints on how, say, a house should be built, so DNA sequences, genes or genomes are blueprints on how proteins or even whole cells or organisms should be built.

As Claire Ainsworth said in 2015, “[a]sk me what a genome is, and I, like many science writers, might mutter about it being the genetic blueprint of a living creature. But then I’ll confess that ‘blueprint’ is a lousy metaphor since it implies that the genome is two-dimensional, prescriptive and unresponsive.” And many modern biological experts would agree, especially Philip Ball in his book How Life Works. But for a while that metaphor was used as a, I’d argue, rather fruitful, tool for thinking about genetics.

As early as 1955, a couple of years after the discovery of the structure of DNA, George Gamow, a theoretical physicist, cosmologist and molecular biologist, wrote:

“Comparing a living cell with a factory, we can consider its nucleus as the manager’s office and the chromosomes as the filing cabinets where all the production plans and blueprints are storied. The main body of the cell, its cytoplasm, corresponds to the factory area where workers are manufacturing the specified product from incoming raw materials. The workers in a living cell are known as enzymes. They extract energy from the incoming food, break down the food molecules and assemble the separated units into various complex compounds needed for the growth and well-being of the organism.” (Gamow, 1955: 70)

The complexity (and dynamics) of the living blueprint metaphor was bleached out of it over time, leaving us with a conventional or rather dead metaphor, but one that still works in the context of science communication with regard to, say, advances in therapies for haemophilia.


But what about the fleet of microscopic postmen? That’s surely a totally new metaphor, one would think. But is it?

Looking at it more closely, one can see that this metaphor harks back to images of tiny robots, from surgeons to submarines, swimming around in the human body doing useful repair work.

More precisely, this metaphor is rooted in a lecture given by the physicist Richard Feynman in 1959 entitled “There is plenty of room at the bottom”. In this lecture he introduced the concept of a tiny, swallowable surgical robot. The lecture is, by some, regarded as the beginning of nanotechnology and nanomedicine (although that is disputed by others). It might also have inspired the 1966 film Fantastic Voyage (where a submarine and its crew are shrunk and injected into the bloodstream of a scientist when a blot clot renders him comatose) – and with this we are perhaps back to the ‘fleet’ part of Gallagher’s metaphor….Anyway… Feynman wrote:

“A friend of mine (Albert R. Hibbs) suggests a very interesting possibility for relatively small machines. He says that, although it is a very wild idea, it would be interesting in surgery if you could swallow the surgeon. You put the mechanical surgeon inside the blood vessel and it goes into the heart and ‘looks’ around. (Of course the information has to be fed out.) It finds out which valve is the faulty one and takes a little knife and slices it out. Other small machines might be permanently incorporated in the body to assist some inadequately-functioning organ.”

As this passage shows, Feynman’s (and Hibbs‘) surgeon, unlike the postman evoked by Gallagher, has a rather hands-on approach – we are dealing with surgery after all – not with the rather more abstract process of building proteins by delivering ‘letters of instruction’.

But both the surgeons and the postmen have to be conveyed to where they are needed and that’s where engineered viruses or so-called ‘viral vectors’ come in. These are modified viruses designed to deliver genetic material into cells.

Metaphors as viral vectors

But that’s not something that’s easy to imagine. Codes, instructions, blueprints and postmen work much better for that. These metaphors might be old, contested, worn out or polished up – they work. Why? Because they are viral cultural vectors, so to speak. They carry cultural and scientific payloads to your brain and, more importantly, your imagination.

This reminds me of Jon Turney’s 1998 book Frankenstein’s Footsteps. In this book Turney explored the role of popular culture in helping to shape public attitudes towards advances in genetics and genomics. He suggested that just the title of a cultural reference, such as ‘Frankenstein’ can evoke an entire story or ‘script’, which can then be used as an interpretative frame.

In the same way, metaphors, like ‘blueprint’ or ‘postmen’ evoke interpretative frames and scripts. The funny thing is that you don’t have to know the script, that is, you don’t actually have to have read the works of Mary Shelly or Gamow or Feynman to think that you have got some understanding of a very complex issue. That comes in quite handy in science communication. In this way metaphors can be quite magical, for good or for ill.

Image: Postmen leaving from Christchurch, NZ, central postoffice, c. 1900 (I couldn’t find postmen in boats, so bicycles it is)

Posted in Metaphors