What are the properties of DNA?

DNA is the hereditary material found in almost all prokaryotes and eukaryotes. It is composed of two helical strands that are wound around the same axis. DNA helices may be right handed or left handed.

DNA is polar in nature because of its highly charged phosphate-sugar backbone. Its polarity renders it soluble in water. However it is insoluble in the presence of salt and alcohol. 

DNA bases are capable of absorbing UV light at 260 nanometers. The amount of UV light absorbed increases with the order of bases. 

DNA denatures on being subjected to high temperatures. The heat disrupts the hydrogen bonds between the bases, causing the two strands of DNA to unfold and separate from each other completely. The temperature at which DNA denatures is known as melting temperature or Tm. 

The melting temperature is specific for each specific sequence. The region with higher concentration of C-G has a higher melting temperature. This is because more energy is needed to break the 3 hydrogen bonds that bond these bases. The regions with higher concentration of A-T have a lower melting temperature as it is bonded with only 2 hydrogen bonds.  

On cooling the two separated strands join each other again. This process is called renaturation.