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Tuesday, February 10, 2009

some things i would never have admitted not knowing....

"wow," i exclaimed."that looks really pretty!"
cut away from the world honking away on the roads below,a group of 8 students sat listening to their professor enthrall them about the magic of cytogenetics. we sat in this laboratory tucked away in one corner,on the 7th floor of a massive hospital. the curly haired(somehow,she reminded me of einstein) doctor teaching us,looked at me and smiled kindly,"yes,it sure is,kid. for the simple reason it is a normal,healthily propagating cell and not cancer."
well, the slide that took my breath away was a slide on a technique called "chromosome painting."(i know,somehow the vast reaches of the human brush leaves me stunned,heehee.)

i guess,i am writing this blog,just a few months away from my final examination,because i want to be honest,with myself,with my friends,my family and all the people who think that when someone passes their postgraduation examination they know everything about whatever subject they have passed out in.well,ideally they should. but well,frankly,i donot. what i am going to write will make more sense to my friends when they read it.
i want to confess a few things i never have said before.
i want to confess that it took me a few years to completely understand what a genome means and that too after rote learning about the human genome project ,and spewing it in the answer sheets.
here goes,
everyone knows we are made up of cells.
basic science teaches us that the cell has a few stuff inside it,one of it is the nucleus.
the nucleus (as one of my teacher explained) is the secured locker of a bank,containing the valuable information of our heredity.
well,here is a bit more of pre degree biology.
the stuff inside our bank lockers have been deposited by our parents,and that too in exact halves(i am talking about normal conditions,if we can call oursleves normal!). its is a beaded,threadlike stuff called chromatin. when a cell divides,(that should happen if we have to grow.) this threadlike structure become something which we see as stickmen.scientifically they are termed 'chromosomes'. its on this stickmen that is written the story of our lives.our "genes."
i want to say that to figure this out,clearly,it took me some time.i never knew whether genes make up DNA or DNA make up genes.
well,yea..DNA..its like the house and -genes,chromosome,chromatin....bricks- DNA.
it stands for Deoxyribo Nucleic Acid and is the biomolecule which decides how we turn out.
now,back to chromosomes. well,we have a definite number of stickmen in us. we human beings have 23 pairs.that is 46 stickmen(lets stick to normal,guys!).i donot want to go into other species.but yes,just that we know,the numbers are different in different species,but constant in the same species.
so,these 46 stickmen come from our parents cells-well,they have names too,mr.sperm and ms(soon to be mrs) egg-at the time of the phenomenon called fertilization(another blog will be dedicated to this).
now,graduating to degree biology where this branch takes the fancy name of genetics. we were taught "humans are diploid". simple and precise as i can try...ploidy is the number of sets(homologous...similar,etc)chromosomes in a cell. and haploid is the number of chromosomes in the gametes(remember mr sperm and ms egg-they are called gametes,like men and women can be called people).
so now,diploid is two times haploid,triploid is three times,tetraploid is 4 times and so on.
so if,n=haploid,2n=diploid,5n=pentaploid.......
one n=23 comes from mummy,one n=23 comes from daddy.
now comes the culmination of this..when i knew what a "genome" was.....
when both the "n" from mummy and daddy combine,they produce a 2n which is a new colour..a new individual..a new us..
this new individual has 2n..but the "n"s making up the 2n are different from mummy "n" and daddy "n" for the simple fact that they have mixed and produced the 2n.they have merged and made the new combination and not just come and settled down next to each other.
the image below is of a technique called karyotyping..lets just say..we looted a dividing cell and have arranged the loot for visual appreciation. these are the stickmen i was talking about. our chromosomes arranged in pairs. and yea..that X and Y ,you see are the sex chromosomes. this is a male karyotype(normal).females will have 2 X instead of XY.

in each single pair,if we take one chromosome and make a set of 23...we have the GENOME.
some points:
each chromosome have similar we pick one from each pair..we are representing the whole.
though they are from our parents they are not the identical ones..that is if we arrange 23 chromosomes we will not get our parents genome,i hope i have made that point clear.
well...thats what it is..all our cells have 46 chromosomes.
so if we pick up one cell and take 23(which is our "n"...haploid..remember?) representatives,one from each pair..we have our GENOME.

phewww....i hope we understood the "great G".
these were terms which were vague to me..but i hope with passing becomes clearer.
and yea..i remember now i started with chromosome painting,well there is chromosome walking ,jumping and much more.but..i guess..some other day..i will confess and try to decode it.
till then...enjoy our amazing GENOME.
and yes...doubts and corrections are welcome.

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