If you know how many base pairs a DNA molecule has,
then you can calculate the length - so I hope you
like to do some math!
If we assume that
when you stretch the DNA out into a straight line,
it still retains the typical B-form helix
structure, and that a single human genome contains
about 3 billion base pairs (3 x 109),
then we get the following:
pairs) x (3.4 angstroms per base pair) =
10,200,000,000 angstroms long
Now, 1 angstrom is equal to 0.0000000001 meter.
length of the human genome is about: 1.02 meters
or around 40 inches
On the other hand, the
diameter of DNA is around 2 nanometers (nm).
That's two billionths of a meter, or
atoms are 0.1-0.2 nm in diameter. The common
cold virus is a sphere 30 nm across. Brightly
colored soap bubbles are about 100-400 nm
As you know eucaryotic cells contain
a very large quantity of DNA (human cells have at
least a thousand times more DNA than a typical
bacteria cell). E.coli chromosomes have about
4.7 x 106 base pairs which results in a
length of 1.6 mm. An E.coli cell, however is only
0.002 mm long . That explains why the DNA must be
folded in order to fit into the cell.
length of DNA in eucaryotic cells is so great that
the risk of entanglement and breakage becomes
severe. That is the reason why histones
(proteins unique to eucaryotes) bind to DNA and
wrap it up into compact and manageable
chromosomes. (a human egg cell, which is a large
cell actually, is about 0.08 mm in diameter.
That's why the 1000 mm long DNA is wrapped up and
divided into 23 chromosomes to make it fit).
hope this answers your question.
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