When you read about human genetics, three fundamental concepts you will come across are: the gene, the chromosome and the DNA. When I first encountered the topic, I could mostly understand what each term meant, but I struggled to distinguish them precisely. That was until I came across a fantastic analogy in the book ‘The Selfish Gene’.
I’m recounting below the book’s passage (edited for brevity).
There are about a thousand million million cells making up an average human body, and, with some exceptions which we can ignore, every one of those cells contains a complete copy of that body’s DNA. This DNA can be regarded as a set of instructions for how to make a body, written in the A, T, C, G alphabet of the nucleotides. It is as though, in every room of a gigantic building, there was a book-case containing the architect’s plans for the entire building. The ‘book-case’ in a cell is called the nucleus. The architect’s plans run to 46 volumes in humans—the number is different in other species. The ‘volumes’ are called chromosomes.
I shall make use of the metaphor of the architect’s plans, freely mixing the language of the metaphor with the language of the real thing. ‘Volume’ will be used interchangeably with chromosome. ‘Page’ will provisionally be used interchangeably with gene, although the division between genes is less clear-cut than the division between the pages of a book.
The 46 chromosomes consist of 23 pairs of chromosomes. We might say that filed away in the nucleus of every cell are two alternative sets of 23 volumes of plans. Call them Volume 1a and Volume 1b, Volume 2a and Volume 2b, etc., down to Volume 23a and Volume 23b. Volumes 1a, 2a, 3a, … came, say, from the father. Volumes 1b, 2b, 3b, … came from the mother.
For instance, Page 6 of Volume 13a and Page 6 of Volume 13b might both be ‘about’ eye colour; perhaps one says ‘blue’ while the other says ‘brown’. Sometimes the two alternative pages are identical, but in other cases, as in our example of eye colour, they differ. If they make contradictory ‘recommendations’, what does the body do? The answer varies. Sometimes one reading prevails over the other. In the eye colour example just given, the person would actually have brown eyes: the instructions for making blue eyes would be ignored in the building of the body, though this does not stop them being passed on to future generations. A gene that is ignored in this way is called recessive. The opposite of a recessive gene is a dominant gene. The gene for brown eyes is dominant to the gene for blue eyes. A person has blue eyes only if both copies of the relevant page are unanimous in recommending blue eyes. More usually when two alternative genes are not identical, the result is some kind of compromise—the body is built to an intermediate design or something completely different.
Observe the equivalence the analogy makes.
● Page — Gene
● Book — Chromosome
● Book Case — Nucleus
● Room — Cell
● Building — Human Body
● Architect — Evolution
Notice how the concept intuitively builds from the ground up— from the smallest segment (gene) to the overarching concept (evolution). Once you get the analogy, it’s difficult to not grasp the concept. Few years down the line, you may forget the names of the nucleotides (A,T,C,G) but I bet you will remember how gene expression works.
That’s the power of a great analogy. It can unbundle the most complex of topics and make it accessible and comprehensible to any curious person.
The second one is from Professor Karthik Muralidharan. Through a football game analogy, he argues why the state needs to play a central role in providing quality education to everyone.
I am paraphrasing his argument.
A lot of us would share a world view that says that the role of the genetic lottery in life outcomes should be minimised to the extent possible. As an analogy, imagine life as a football field. The field in its original shape is uneven. Therefore ideologies such as socialism, communism argue that because the field is uneven, the game should be a draw.
But if the game is a draw, there’s no incentive to play and there are no spectators and no economy. You shrink all activity. What we would like to do is to level the field as much as possible and then allow people to go play and let the natural kind of balance emerge so that everyone gets to keep the fruits of his/her labor.
However, I think there is a fundamental tension here. We want people to keep the fruits of their labor, but we should also mitigate the amount of intergenerational transmission of inequality.
The problem is what people seem to do the most with their money is propagate their advantage to their offspring. Think of what people do in terms of schooling, health etc., for their children. So I think the role of the state in the provision of basic services of health and education, is much more fundamental. It must provide quality health and education so that, we get to establish the kind of level playing field to mitigate the intergenerational inequity.
Just brilliant. With use of a simple analogy, Professor Karthik makes a case for equity with remarkable clarity.
Analogies are incredible tools to illuminate the new through the old. They take what is already known and help our brains make similar connections with the new concept. Perhaps in our academic books and school texts, it helps to have more analogies to decrypt concepts rather than inundate readers with jargon.
Lastly, a word of caution. Analogies can only go so far and it’s important to distinguish good analogies from bad ones.
A good analogy is like a GPS map. It doesn’t fully correspond to the actual territory, but helps you navigate deftly from point A to point B.
On the other hand, a bad analogy…. A bad analogy is like a glass of water.
sir you conveyed a valuable information in a great way….hatsoff to you and keep sharing your wonderfull ideas & learnings…..reading your articles makes to think and act accordingly.
Thank you sir! Sir please write a post on how to develop a mindset and routine/habits for success in UPSC and your experience with them.
I like the way you left the bad analogy example without an analogy 😉
That ending. Pure gold! 😀
Sir ,if possible from your experiences
Write on the Importance of Consistency .
Thanks for the Analogy one.
Thank-you sir for such a wonderful Article.
But i have doubt on other topic that ,
How to manage/cover current affairs news for optional ?
Awesome writing skills ?
Splendid Article!
ending superb
I truly appreciate your writing skills. This one is a gem!
The ending couldn’t have been better ☺️
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Sir could you please share your time table while you were preparing and working together.
It may not provide the best time table for an aspirant like but can be very helpful to get some idea how to go about the very preparation of this exam. I am not appearing for 2020 and 2021 is my last attempt!!
thanku sir anudeep, after long time with a great topic i love to read n was anxiously waiting for this for the long time
THANK YOU SIR….you always play a prominent role in my preparation.
amazing ending ……:)
PISTIL – GENE
PETAL – DNA
FLOWER – NUCLOUS
STEM – CELL
PLANT – HUMAN BODY
ARCHITCT – EVOLUTION
ANNA AM I CORRECT
punch like a one-inch punch.
Nice one.
However, the book (or the volume) refers to the chromosomes, and not DNA, as mentioned by you in the numbered list. The nucleotides would be the letters, DNA- the words, Genes- the pages, Chromosomes- the book/volume, Nucleus- the book case, and so on.
Corrected. Thanks!
Then the smallest fragment would be nucleotide right
Sir, your blog post are much helpful.. Happy to see you after a long time ?
Brilliant Anudeep!
Wow sir!!
Thanku so much sir … ur blog posts r vry helpful …… sir pls recommend basic books for anthro. From upsc perspective … sir pls do post if u get tym out of ur busy schedule ….. thanku
Amazing… Thank you sir…
Wow sir
So eloquently you explain this concept
Love your writing skill….
Thank you for sharing your thoughts with us…
Wow sir
So eloquently you explain this concept
Love your writing skill….
Thank you for sharing your thoughts with us…
Very well said Anudeep & thank you for sharing your views on “Analogies as thinking tools”. I think if we understand the concept of any topic, we can analyze and connect in an easy way with the day to day life. I just loved how you analyzed the topic with page, book,bookcase, room,building, architect. Awesome if every teacher explains the content using analogies , learning becomes fun & connective. ?? ?
When you are on the death, what the knowledge of genetics and gene expression helps … Know who really you are??? Life is beyond genes and gene expression… Meeru indian ayi “Selfish gene” Books chaduvtaaru.. Chadavandi…What about death and life.. Sperm and ovum meet avutane life start avvali
Enduku? .. Think… Upanishads open cheyyandi sir.. Ooke okate genetics pattukoni velaadutaaru.. Nenu genetics student.. Meeru genetics ni deep gaa study chesaaka analyse chesaaka artham avutadi.. Mana indians entante mana Upanishads ni chadavaru.. Foreign author books chaduvutaaru…
This blog post is very knowledgeable and somewhat very interesting. It gives us a different way of analysing concept with more clearity. And u keep on learning so that u can impart it well is very appreciable. Thanks for imparting such knowledgeable things.
Keep writing.
Thank you Anudeep annaya for giving priceless information for us.
Wow sir, Thank you Sir . Your Blog post very helpfull with me thank u sir sharing with us
Brilliant ?