Tooltip Tags: cell nuclei

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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observing a cell nucleus is like revealing invisible writing

An example of an analogy used in a popular science book:

"Each cell contains in the its interior a small spherical body known as the nucleus, which is formed by a fine network of the substance known as chromatin. It must be noticed here that various parts of the protoplasm forming the body of the cell have under normal circumstances equal optical transparencies so that the structure cannot be observed simply by looking at a living cell through a microscope. In order to see the structure we have to dye the material of the cell, taking advantage of the fact that different structural parts of the protoplasm absorb the dyeing materials in various degrees. The material forming the network of the nucleus is especially susceptible to the dyeing process, and appears clearly visible against the lighter background.

You can see a similar method by writing something on a piece of paper with a wax candle. The writing will be invisible until you try to shade the paper with a black pencil. since the graphite will not stick to the places covered with wax the writing will stand out clearly on the shaded background."

George Gamow (1961) One, Two, Three…Infinity. Facts and speculations of science, Revised Edition, Dover Publications, Inc., New York.

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