November 21, 2017 Tuesday
Bedtime Story
Microsatellites or Short Tandem Repeats (STRs)
Last night I had left you with a term that
seems bizarre and outlandish in genetics – microsatellite.
Let me explain that for you.
In genetics, microsatellite is the name that
has been given to tandemly repeating (meaning lying next or adjacent to each
other) DNA motifs that range in length from 2 to 13 base pairs and typically
repeat from 5 to 50 times.
For example the sequence ATATATATATATAT is
a dinucleotide microsatellite that is repeating on our case 7 times.
Now consider another example
CTGCTGCTGCTGCTG.
This would be an example of trinucleotide
microsatellite that is repeating 5 times.
Thousands of such tandem repeats are
littered all over our genome and genomes of our cousins.
As to their function I am not sure since
they are mostly non-coding and hence biologically silent.
They are known to have a higher mutation
rates and hence probably have survival value in that they promote diversity
within species.
STR (short tandem repeats) are a specific
type of microsatellite that are two to thirteen nucleotides long and are
repeated hundreds of time in tandem on a DNA strand.
Suffice it is for us to know that the STR
lengths varies widely in human population and this fact is used by forensic
geneticists to compare two DNA samples.
Of course, the distinction is often
statistical and it is not a full proof system but that it not the point here.
We need not worry about its intricate
detail on its accuracy of forensic identification and matching since our story
is not on crime though as you would have noticed, wars often feature in my
stories.
This is so because humans are possibly the
most organized warriors among all the species and like religion, war is there
to stay with us no matter how much “progressive” we consider ourselves to be
with each passing century.
Our current person of interest Gilles
Vergnaud was forced to venture into forensic genetics but he used it to
differentiate and characterize not humans but microbes.
He was particularly interested in the
dangerous pathological (to humans) microbes that cause anthrax (Bacillus anthracis)
and plaque (Yersinia pestis) and for that very reason could be used as
biological weapons by Saddam Hussein, in those days enemy number one of the
Western world.
It is a fact that like many other nations
Saddam Hussein too had launched a program of biological weapons in the early
1980s.
His biological weapon (BW) program included
far more organisms than the above two; in fact his BW program included five
strains of bacteria, one strain of fungus, five viruses and four toxins
including botulinum toxin and aflatoxin.
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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