Comparisons – Page 18 – Science-Education-Research

inactivated X chromosome is like a towel twisted till it is a millimetre in length

An example of a quantitative comparison with an everyday example used in popular science writing:

"When an X chromosome is inactivated, it adopts a very unusual physical conformation. The DNA becomes incredibly compacted. Imagine you and a friend each take hold of opposite ends of a towel. You start turning your end of the towel clockwise, and you friend does the same at the other end. Pretty quickly, the towel will start twisting in the middle, and the two of you will be pulled closer together. Now imagine that the towel is about five metres in length, but you manage to keep twisting it until it's a dense slump of towel only a millimetre in linear length. By this stage, the towel is extraordinarily tightly would up. Essentially, the X chromosome becomes as tightly compacted as that towel."

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

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spindle apparatus that does not disassemble is like a fire appliance with its ladder extended

An example of an analogy used in popular science writing:

"There are drugs that interfere with the way in which the spindle apparatus pulls the replicated chromosomes to opposite ends of the cells. The spindle apparatus is formed by the coming together of a large number of proteins, and these only combine at the time when a cell is ready to pull the chromosomes apart. A drug called paclitaxel works by making the spindle apparatus too stable so that the complex of proteins can't disaggregate.

We can visualise why this is a bad thing for a cell by comparing the scenario with one of those fire engines that carries an extending ladder. It's great that the ladder can be extended to rescue people from upper storeys of a burning building. But if the fire crew can't get the ladder folded back down again after the emergency and have to drive around with it fully extended, it won't be long before they have a pretty serious accident. The same happens in the cells treated with paclitaxel. Systems in the cell recognise that the spindle apparatus hadn't been deactivated properly, and this triggers destruction of the cell."

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.

{paclitaxel is an anticancer agent produced naturally by fungi that are symbionts of some trees}

spindle apparatus has something to hang on to when trying to pull the chromosomes apart

An example of anthropomorphism in popular science writing:

"The CENP-A [Centromeric Protein-A] in these thousands of octamers at the centromeres gives the spindle apparatus something to hang on to, when it's trying to pull the chromosomes apart. One of the effects of inserting CENP-A into the octamers is that it makes the centromere regions more rigid. If we think about trying to pull a blob of jelly, compared with a boiled sweet, it's obvious that the increased rigidity will be an advantage for the action of the spindle apparatus."

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

This is metaphorical, as the spindle apparatus does not have intentions.

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Many examples of anthropomorphism are listed in 'Creative comparisons: Making science familiar through language. An illustrative catalogue of figurative comparisons and analogies for science concepts'. Free Download.

That the spindle apparatus is rigid, more like a boiled sweet than a blob of jelly, seems intended as an analogy, although the mapping seems to swap what is considered being pulled. However, from a Newtonian perspectives, forces are always mutual, so if the boiled sweet (spindle apparatus) is being pulled, then so is the chromosome.

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extracellular matrix is a sort of wallpaper paste

An example of a simile used in popular science writing:

"Fibroblasts are found in a wide range of human tissues. They secrete something called the extracellular matrix, a sort of thick wallpaper paste that holds the cells in position."

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.

DNA is wrapped up like carefully stored Christmas lights

An example of analogy used in popular science writing:

"But, if you are a freakishly organised person, you will wrap each string of [Christmas] lights around a piece of cardboard before storing them away. And your organisational acumen will be rewarded next Christmas when you take the lights out of he surprisingly small box you are able to use for storage. Not only did you save on loft space, you also will find that it's very easy go unwind the lights, none of the strands get tangled around each other or snapped, and you can access your one favourite bulb very easily.

The same process happens in our cells. DNA is not stored as a random bundle of scrunched-up genetic material. Instead it is wrapped around certain proteins.This stops the DNA getting tangled and broken, allows it to be squeezed in an orderly fashion into a small space, and also keeps it structured so that the cell can access different regions as necessary, in order to switch individual genes on or off.

The DNA in our cells is wrapped around particular called histones … Eight histone proteins – two each of four different types – form an octamer. DNA wraps around this octamer, like a skipping rope around eight tennis balls."

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

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nuclear DNA is like something the height of Everest packed into a golf ball

An example of an everyday comparison used in popular science writing:

"If you stretched out the DNA from one human cell it would reach for two metres, assuming you joined up the material from all the chromosomes. But this DNA has to fit into the nucleus of a cell, and the nucleus has a diameter of just one hundredth of a millimetre.

This is like trying to fit something that is the vertical height of Mount Everest in to a capsule the size of a golf ball."

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

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proteins build up from CENP-A like adding LEGO bricks in a particular order

An example of analogy and simile used in popular science writing:

"The critical feature of the centromere is that it acts as a location for the binding of the protein called CENP-A (Centromeric Protein-A).

… CENP-A acts as a foundation stone….

The CENP-A acts as the essential cornerstone for the recruitment of all the other proteins that are required for the spindle apparatus to do its job. When a cell is actively dividing, over 40 proteins build up from the CENP-A . They do so in a step-wise fashion, like adding on LEGO bricks in a particular order. Immediately after the duplicated chromosomes have been pulled to the opposite ends of the cell, this big complex falls apart again….Normally, the nucleus has a membrane around it, and large protein molecules find it really difficult to get through this. When the cell is ready to separate its replicated chromosomes, this barrier breaks down temporarily and the proteins can join on to the complex at the centromere. It's like having a removal company outside your house. they are ready to shift you furniture but can't get on with the job unless you open the door and let them in."

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

There are two different analogies here: Lego bricks as proteins in building up the complex; the removal company as like proteins that cannot be added to the complex whilst the nuclear membrane is in place.

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There are also similes for the CENP-A protein as being like a foundation stone, or cornerstone.

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The phrasing "molecules find it really difficult to get through" could be seen as an example of anthropomorphism, as molecules have no awareness of where they are (and have no intentions or desires regarding entering the nucleus).

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social media follower count is like the cosmic microwave background radiation

An example of a simile from social media drawing upon a scientific notion:

"Many philosophers have around 2k followers because we were in a popular starter pack when people started rebuilding the philosophy community here. Our follower count is like the cosmic microwave background radiation, a faint relic of random past events."

Prof. Manolo Martínez, University of Barcelona, posting on Bluesky‬ ‪@manolomartinez.net

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chromosomes have their own aglets that maintain the integrity of genomes

An example of analogy in popular science writing,

"At either end [of show laces] there is a little cap made from metal or plastic. This is called the aglet, and it stops the lace from unravelling and fraying. Our chromosomes have their own aglets, and these are extremely important for maintaining the integrity of our genome.

These chromosomal aglets are called telomeres and they are made from a form of junk DNA that we have known about for many years, plus complexes of various proteins."

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

By itself the reference to aglets in the chromosome would be a metaphor, but in the context this is clearly presented as an analogy.

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some retroviruses are now genomic fossils

An example of metaphor in popular science writing:

"Long ago in our evolutionary history, some retroviruses became fully established in our genomes. Many are now genomic fossils, and so they can never again produce viral particles. But some still contain all the components required to make new viruses. These are normally kept under very tight control by the cell."

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 metaphors are listed in 'Creative comparisons: Making science familiar through language. An illustrative catalogue of figurative comparisons and analogies for science concepts'. Free Download.

foreign DNA elements are a kind of fossil record

Examples of figurative language used in popular science writing:

"…the human genome…was invaded by foreign DNA elements, which then multiplied hugely in number, finally becoming stable integral parts of our genetic heritage. These foreign elements act as a kind of fossil record in our genome, which can be compared with the records from other species.
…
When the draft human genome sequence was released, it was astonishing to realise just how widely these genetic interlopers have spread through our DNA."

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

"A kind of fossil record" is a simile as the comparison is marked.

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As commonly happens with similes, the subsequent reference to 'the records' is not marked and so would of itself be a metaphor without this context.

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The notion of DNA elements invading the human genome reflects the common metaphorical military language used about infection (read 'Disease and immunity – a biological myth'). Seeing these DNA elements as 'foreign' and 'interlopers' reflects a particular perspective on the evolution of the genome that sees certain elements as properly part of our inheritance and others as in some sense improper. (This is a bit like seeing people whose ancestors invaded your country from some foreign countries as proper citizens but those ancestors arrived peacefully more recently as not belonging.) Clearly a different perspective is possible that sees extant human genomes as having a complex development drawing on multiple sources that are all seen as contributing.

There is a parallel in this use of language with the way early Homo sapiens may be described as human ancestors when other hominids which successfully bred with them (Neanderthals, for example) and so are the source of some elements of modern human genomes, are not described as our ancestors! (Read 'Can ancestors be illegitimate?'). This is a bit like crossing your great-great grandfather off the family tree because your great-great grandmother married beneath herself!

stacked human cells scaled to a banknote would reach beyond the moon

An example of an everyday comparisons used in popular science writing:

"An adult human is composed of about 50-70 trillion cells .That's a lot of cells to visualise, so try it this way. If each cell was a dollar bill, and we stacked 50 trillion dollar bills on top of each other, they would stretch from the Earth to the moon and halfway home again."

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

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