November 05, 2017 Sunday
Bedtime Story
Analyzing the 2002 Ruud Jansen Paper
This 2002 paper that I left you with last
night was a major advancement from the past papers as it showed for the first
time the existence of some other genes along with the cluster repeats.
Since these genes came along and always
accompanied the CRISPR repeats, Ruud Jansen simply called them CRISPR
associated system or cas in short.
I want to stress upon you the following
four lines of the paper:
“The presence of multiple chromosomal
CRISPR loci suggests that CRISPRs are mobile elements.
Four CRISPR-associated (cas) genes were
identified in CRISPR-containing prokaryotes that were absent from
CRISPR-negative prokaryotes.
The cas genes were invariably located
adjacent to a CRISPR locus, indicating that the cas genes and CRISPR loci have
a functional relationship.
The cas3 gene showed motifs characteristic
for helicases of the superfamily 2, and the cas4 gene showed motifs of the RecB
family of exonucleases, suggesting that these genes are involved in DNA
metabolism or gene expression.”
Each sentence is of utmost importance as
each one is a new factual statement that has a significant bearing on the
unfolding of the whole CRISPR story.
The first sentence stresses upon the
mobility of the prokaryote repeat cluster.
It gave the future or the parallel
researchers a hint that its source could be extramicrobial (I think I may have
just coined a new word).
The second sentence is a discovery of
something absolutely new; a set of homologous genes that always accompany
CRISPR clusters and that Ruud Jansen in the paper named cas genes.
The third sentence is a speculation
associating the close proximity of the two systems with some sort of functional
relationship between them.
Of course, the function itself was never
stated as it was then not known.
But lastly and crucially, Jansen et al
mentioned an extremely important finding that could direct other genetic
microbiologists what further to look for.
The finding was that these cas genes
demonstrated helicase and nuclease motifs.
Now I need to tell you a little about these
two enzymes as well.
Yet before I go to tell you about the
enzymes, there is this interesting word that caught my eye – motif.
Motif is general English can refer to a
pattern, a design, a structure or even a logo.
But a motif in biochemistry and genetics
has a very specific meaning.
Motifs in biochemistry are of two types –they
can either be structural motif or sequence motif.
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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