November 12, 2017 Sunday
Bedtime Story
The Source of the Spacers in the Repeat-Spacer Array of CRISPR genes
I have already digressed too far from my
story on the CRISPR/Cas system where I was describing helicases and nucleases
enzymes.
Ruud Jansen in his 2002 paper had stated
that the cas genes demonstrated helicase and nuclease motifs.
Helicases unwind and unpack the genes lying
in the entangled chromosomes.
It is only after the unwinding of the coiled
chains can such important processes such as DNA replication, transcription,
translation, recombination, repair and ribosome biogenesis can take place.
So important and vital are these helicases
to the functioning of cells that in eukaryotes approximately 1% of the total
genes are devoted totally to the production of this particular family of
enzymes.
The cas genes discovered by Ruud Jansen was
also one among the several helicases.
After this paper, the next major
advancement related to this field came three years later from not one place but
three independent laboratories.
2005 saw publication of three papers totally
independent of each other in three different journals from three different labs
that added another piece to the puzzle.
They all suggested that the spacers in the
repeat-spacer array of CRISPR genes are foreign and not derived from the
chromosome of the organism.
In fact they were more specific and made a
claim that the spacer genes were derived either from phage DNA or plasmids.
A phage or a bacteriophage is to bacteria
as pathogenic bacteria are to us; Bacteriophages are viruses that attack
bacteria, infect them, replicate inside them and eventually destroy them.
It is believed that they are the most ubiquitous
organisms on this planet, far outnumbering even bacteria.
They are found anywhere where their hosts
bacteria exists, but the most dense source of these viruses is the sea water.
Furthermore it is estimated that almost 70%
of the bacteria in marine water are infested with bacterophages which I think
is not very different from the relationship that exists between bacteria and
other living beings on the planet.
There is something interesting that needs
to be told regarding the discovery of these phages.
I remember as a small boy when one Sunday my
parents took me and my brother on a boat ride on the river Ganges, that to most
Hindus is very sacred, a comment from the boat man:
You can drink water directly from the
river.
The river water is drinkable and will not
cause disease as it is holy and sacred.
I am deeply skeptical of such claims but it
seems that there indeed was some truth to the statement being made by the
boatman, at least then (now it is polluted beyond all limits).
Stay tuned to the voice of an average story storytelling
chimpanzee or login at http://panarrans.blogspot.com
Good night mon ami and my fellow cousin ape.
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Another great educator and a teacher that I am aware of is
Professor Subhashish Chattopadhyay in Bangalore, India.
While I narrate stories, Professor Subhashish an electronic
engineer and a former professor at BARC, does and teaches real mathematics and
physics.
He started the participation of Indian students at the
International Physics Olympiad.
Do visit him here:
All his books can be downloaded for free through this link:
For edutainment and English education of your children, I
recommend this large collection of Halloween Songs for Kids:
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