An example of metaphor and analogy in popular science writing:
"Imagine a written script for a play, or film, or television programme. It is perfectly possible for someone to read a script just as they would a book. But the script becomes so much more powerful when it is used to produce something. It becomes more than a string of words on a page when it is spoken aloud, or better yet, acted.
DNA is rather similar. It is the most extraordinary script. Using a tiny alphabet of just four letters it carries the code for organisms from bacteria to elephants, and from brewer's yeast to blue whales. But DNA in a test tube is pretty boring. It does nothing. DNA becomes far more exciting when a cell or an organism uses it to stage a production. …
Thousands and thousands of regions of junk DNA are suspected to regulate networks of gene expression. They act like the stage directions for the genetic script, but directions of a complexity we could never envisage in the theatre."
Nessa Carey (2015) Junk DNA. A journey through the dark matter of the genome. London: Icon Books Ltd.
There are several different metaphors here. The alphabet of four letters (i.e., the four bases) and seeing the genome as carrying a 'code' (though both of these metaphors are so commonly used that they might be considered 'dead metaphors' – as many readers will already be familiar with these comparisons.).
Read about metaphor in science
Read about examples of science metaphors
Many examples of science metaphors are listed in 'Creative comparisons: Making science familiar through language. An illustrative catalogue of figurative comparisons and analogies for science concepts'. Free Download.
To describe DNA as a script could also be seen as a metaphor. However the preamble about the nature of scripts sets this up as an analogy. An analogy has a mapping between parallel structural features of the target (here: DNA) and analogue (here: script).
So, again, by itself, the reference to DNA being used to 'stage a production' would be seen as a metaphor. However here it is an extension of the same metaphor, meant to be understood as part of an analogy: a script is used in staging a play or other production. In teaching, the teacher should make the mapping of the analogy explicit to learners: but here (in a more informal genre of science communication) the reader is expected to work out what the production refers to.
Read examples of scientific analogies
Many examples of science analogies are listed in 'Creative comparisons: Making science familiar through language. An illustrative catalogue of figurative comparisons and analogies for science concepts'. Free Download.
There is a linguistic problem in discussing DNA as it is not strictly, in a chemical sense, a substance, as (essentially!) each different type of DNA has a different molecular structure, so we might want to say that DNA is not one script but rather that each version of DNA is a distinct script.
