Denaturation of DNA
At high temperatures (950C), the double helical structure of DNA melts due to disruption of base pairing that results in two single strands. This is called as Denaturation of DNA. The temperature at which it does so is called as Melting temperature (Tm). AT rich regions melt faster than GC rich regions. Therefore, Tm is dependent upon the composition of DNA. During denaturation, the absorption of DNA at 260nm increases. This property of DNA is called as hyperchromicity. If the temperature is brought down, the single strands rejoin to form double stranded regions. This is called as annealing of DNA (Fig. 7.8). This property of DNA is exploited in Polymerase Chain Reaction.