As DNA is a macromolecule made up of sugar, phosphates and bases than how can we consider it as a molecule? And secondly which type of experiments we can run to test for the chirality of it? There is one more request, kindly explain it in a little detail and if possible please keep it simple.
I am grateful for your reply, but I was expecting much more explanation.
Thank you.
The DNA molecule, like you said, is a macromolecule, but it is often called just a molecule (and indeed can be considered a molecule from organic chemistry point of view) because it has a definite composition (brutto formula) and specific molecular weight, provided that its integrity is not compromised.
This makes it different from many man-made polymers like polyethylene, where the bulk material is a mixture of the oligomers, and no one can tell exactly what the "molecule of polyethylene" is.
Speaking of chirality - by the definition, chirality is a property of the object (not necessary a molecule) to be not identical to its mirror image. In the case of organic molecules, it means that the chiral molecule cannot be superimposed with its mirror image without breaking the chemical bonds holding it together.
The DNA molecule is of course chiral since, first, it is composed from the chiral elements (sugar parts) and second, it has a spiral secondary structure which is a chiral element itself.
The most common test of chirality is the ability of the chiral molecules to rotate the plane of the linearly polarized light (the degree of rotation depends on the wavelength, look up "optical rotatory dispersion"). Another property of the chiral compounds is the difference in absorption of left and right circularly polarized light (also depends on the wavelength, and is called circular dichroism).
Hope it answers you question.
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