Comparisons – Page 19 – Science-Education-Research

genomes develop as if built from standard LEGO sets

An example of analogy used in popular science writing:

"There are nearly 1,300 gene families in the human genome. Almost all of these gene families occur through all branches of the kingdom of life, from the simplest organisms upwards. …

It's a little as if our protein-coding genome has been built from a giant LEGO kit. …

Throughout evolution, genomes have developed by building out from a standard set of LEGO templates, and only very rarely have they created something completely new."

Nessa Carey (2015) Junk DNA. A journey through the dark matter of the genome. London: Icon Books Ltd.

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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.

cells with the myotonic dystrophy mutation are like cities with riots

An example of an analogy used in popular science writing:

"The proteins that bind to the expansion in the myotonic dystrophy messenger RNA are normally involved in regulating lots of other messenger RNA molecules. … But if these regulators are mopped up by the expansion in the myotonic dystrophy gene messenger RNA, they aren't available to do their normal job. …

Again an analogy may help. Imagine a city where every member of the police force is engaged in controlling a riot in a single location. There will be no officers left for normal policing, and burglars and car thieves may run amok elsewhere in the city. It's the same principle in the cells of people with the myotonic dystrophy mutation. The CTG repeat sequence expansion in a single gene – the myotonic dystrophy gene – ultimately leads to mis-regulation of a whole number of other genes in the cell."

Nessa Carey (2015) Junk DNA. A journey through the dark matter of the genome. London: Icon Books Ltd.

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myotonic dystrophy messenger RNA acts like a kind of sponge

An example of simile (and metaphor) in popular science writing,

"The myotonic dystrophy messenger RNA does something unusual. It binds lots of protein molecules that are present in the cell. The bigger the expansion [of the myotonic dystrophy gene], the more protein molecules that get bound. The mutant myotonic dystrophy messenger RNA acts like a kind of sponge, mopping up more and more of these proteins … [that] are normally involved in regulating lots of other messenger RNA molecules."

Nessa Carey (2015) Junk DNA. A journey through the dark matter of the genome. London: Icon Books Ltd.

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Many examples of science similes are listed in 'Creative Comparisons: Making Science Familiar through Language. An illustrative catalogue of figurative comparisons and analogies for science concepts'. Free Download.

Read about metaphor in science

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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.

fragile X syndrome mutation is like snow covering roads and railway tracks

An example of an analogy in popular science writing:

"In the UK, a relatively small amount of snow can incapacitate the transport networks. The snow covers the roads and the railway tracks preventing cars and trains from moving. When this happens, people can't get to their place of work and this creates all sorts of problems. Schools can't open, deliveries aren't made, banks can't dispense cash, etc. One starting event – the snow – has all sorts of consequences because it ruins the transport systems in society. A similar thing happens in Fragile X syndrome. Just like the snow on the roads and railway tracks, the effect of the mutation is to mess up a transport system in the cell, with multiple knock on effects."

Nessa Carey (2015) Junk DNA. A journey through the dark matter of the genome. London: Icon Books Ltd.

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gene mutation acts like a document with pages glued together in a photocopier

An example of an analogy used in popular science writing:

"A normal gene contains from five to 30 GAA repeats but a mutated gene contains from 70 up to 1,000 repeated GAA motifs. … The big GAA expansion acts as a 'sticky' region, which prevents good copying of the DNA. It's analogous to trying to photocopy a 50-page document, when pages four to twelve have been glued together. They won't feed into the copier, and the process grinds to a halt, for that particular document. In the case of the Freidreich's ataxia gene, no copying means no RNA, which means no protein."

Nessa Carey (2015) Junk DNA. A journey through the dark matter of the genome. London: Icon Books Ltd.

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DNA is like a railway track

An example of simile used in popular science writing,

"DNA is formed of two strands joined together via pairs of bases. We could visualise this as looking a little like a railway track. The two rails are held together by a base on one rail linking to a base on the other side, as if the bases were holding hands. They only link up in a set pattern. T holds hands with A, C holds hands with G."

Nessa Carey (2015) Junk DNA. A journey through the dark matter of the genome. London: Icon Books Ltd.

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Of themselves, the statements that "T holds hands with A [and] C holds hands with G" can be seen as metaphors (where the reader has to appreciate that a figure of speech is being used), but this idea has already been introduced marked as a comparison in the simile ("as if the bases were holding hands").

DNA is a simple alphabet of just four letters

An example of an extended metaphor used in science writing:

"DNA is an alphabet, and a very simple one at that. It is formed of just four letters – A, C, G and T. These are also known as bases. But because our cells contain so much DNA, this simple alphabet carries an incredible amount of information."

Nessa Carey (2015) Junk DNA. A journey through the dark matter of the genome. London: Icon Books Ltd.

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This is a metaphor (not a simile or analogy) as the text suggests not that DNA is in some way like an alphabet, but rather that it is an alphabet. DNA stands for dioxyribonucleic acid, a class of chemical substances not a system of symbols, so the identity is not, literally, accurate. A reader has to appreciate a comparison is being made.

(On the following page, the comparison is referred to as an 'alphabet analogy', and it is suggested that "a gene can be thought of as a sentence of three-letter words'.)

A, C, G, and T are, indeed, four letters but there is then a shift in saying they are also known as bases: they are letters used as symbols for bases, but not actually bases. That is there is ambiguity as A, C, G, and T can stand for four letters in an alphabet or for the four bases that are included in DNA structures, but these are different meanings. So, this is like saying 'a bank is a financial institution; it is also found at the side of a river' or 'a bar is a place where you can buy a drink; it is also an injunction stopping you going there'.

That DNA cannot be identified with an alphabet becomes clear when the text suggests

"because our cells contain so much DNA, this simple alphabet carries an incredible amount of information",

this cannot be sensibly be read as "

"because our cells contain so much [of this alphabet], this simple alphabet carries an incredible amount of information".

Rather, DNA would have to mean something like 'text', i.e.,

"because our cells contain so much [text], this simple alphabet carries an incredible amount of information".

So, we have a kind of category error, as an alphabet and a text are different kinds of things and not synonymous.

DNA scaled to a ladder would reach Mars

An examples of a comparison intended to portray scale:

"Imagine DNA as a ladder, with each base representing a rung, and each rung being 25cm from the next. The ladder would stretch 75 million kilometres, roughly from earth to Mars (depending on the relative positions of their orbits on the day the ladder was put in place)."

Nessa Carey (2015) Junk DNA. A journey through the dark matter of the genome. London: Icon Books Ltd.

(A strand of DNA can in principle, in molecular terms, be very short or extremely long, but the context from which the quote is taken suggests 'DNA' here refers to all the DNA in a single human cell.)

Read about quotidian comparisons

mutation is like a mistake in a knitting pattern

An example of an analogy used in popular science writing:

"Until quite recently, mutations in gene sequences were thought to be important not of because of the change in the DNA itself but because of their downstream consequences. It's a little like a mistake in a knitting pattern. The mistake doesn't matter when it's just a notation on a piece of paper. The mistake only becomes a problem when you knit something and end up with a hole in your sweater or three sleeves on your cardigan because of the error in the knitting code.

A gene (the knitting pattern) ultimately codes for a protein (the sweater).

… The DNA gene is the original knitting pattern. This pattern can be photocopied multiple times, akin to producing the RNA. The copies can be sent to lots of people who can each knit the same pattern multiple times, just like creating the protein. It's a simple but efficient operating model and it works – one original pattern resulted in lots of soldiers with warm feet in the Second World War.

…Researchers showed that when cells contained this expanded repeat, they stopped producing the messenger RNA encoded by the gene. Because they didn't make messenger RNA, they couldn't make the protein either, if you don't send out the copies of the knitting patterns, the soldiers don't get socks."

Nessa Carey (2015) Junk DNA. A journey through the dark matter of the genome. London: Icon Books Ltd.

Carey makes explicit the mapping in the analogy.

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'Downstream' can be considered as a metaphor (as there is no actual stream, so this is a figure of speech).

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some regions of junk DNA are like sleeper agents

An example of simile in popular science writing:

"Other regions of junk DNA are genetic interlopers, derived from the genomes of viruses and other microorganisms that have integrated into human chromosomes, like genetic sleeper agents. These remnants of long-dead organisms carry potential dangers to the cell, the individual and sometimes even to wider populations."

Nessa Carey (2015) Junk DNA. A journey through the dark matter of the genome. London: Icon Books Ltd.

'Interloper' can be seen as a metaphor (actual interlopers are surely acting deliberately) as the reader is told the regions of DNA 'are genetic interlopers', but the 'sleeper agent' reference is marked as a figure of speech.

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junk DNA is like all the Ferrari staff that do not work on the production line

An example of an analogy in public science writing,

"Let's imagine we visit a car factory, perhaps for something high-end like a Ferrari. We would be pretty surprised if for every two people who were building a shiny red sports car, there were another 98 who were sitting around doing nothing. This would be ridiculous, so why would it be reasonable in our genomes? …

A much more likely scenario in our car factory would be that for every two people assembling a car, there are 98 others doing all the things that keep a business moving. Raising finance, keeping accounts, publicising the product, processing the pensions, cleaning the toilets, selling the cars etc. This is probably a much better model for the role of junk in our genome. We can think of proteins as the final end points required for life, but they will never be properly produced and coordinated without the junk."

Nessa Carey (2015) Junk DNA. A journey through the dark matter of the genome. London: Icon Books Ltd.

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DNA is a most extraordinary script

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.).

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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.

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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.