PROPERTIES OF DNA

DNA is a long polymer made from repeating units called nucleotides.In living organisms, DNA does not usually exist as a single molecule, but instead as a pair of molecules that are held tightly together.The backbone of the DNA strand is made from alternating phosphate and sugar residues.A DNA sequence is called "sense" if its sequence is the same as that of a messenger RNA copy that is translated into protein.
DNA can be twisted like a rope in a process called DNA supercoiling.DNA exists in many possible conformations that include A-DNA, B-DNA, and Z-DNA forms, although, only B-DNA and Z-DNA have been directly observed in functional organisms.
DNA usually occurs as linear chromosomes in eukaryotes, and circular chromosomes in prokaryotes. The set of chromosomes in a cell makes up its genome; the human genome has approximately 3 billion base pairs of DNA arranged into 46 chromosomes.
The genetic information in a genome is held within genes, and the complete set of this information in an organism is called its genotype.