Question

What is the physical state of DNA after being denatured by heat?

Short answer

Answer: After DNA has been denatured by heat, its physical state is single-stranded, with the two strands of the DNA molecule no longer held together by hydrogen bonds.

Step-by-step solution

Understanding DNA denaturation

DNA denaturation is a process in which the double helix structure of DNA molecule is separated into two single strands. This occurs when the hydrogen bonds holding the two strands together are broken, which causes the DNA molecule to lose its characteristic structure. Heat is one of the factors that can cause DNA denaturation, as increasing temperature provides more energy for the hydrogen bonds to break.

Effect of heat on DNA structure

When DNA is exposed to heat, the hydrogen bonds that hold the two strands of the double helix together become unstable. As the temperature increases, more hydrogen bonds break, weakening the structure of the DNA molecule. At a certain temperature, called the melting temperature (Tm), the hydrogen bonds are broken and the two strands separate completely. This is known as heat denaturation of DNA.

Physical state of denatured DNA

After the DNA has been denatured by heat, it exists in a single-stranded state. The two strands of the DNA molecule separate and are no longer held together by hydrogen bonds. Since the DNA molecule is still composed of the same nucleotides, its chemical composition remains the same. However, its physical structure has changed due to the absence of the hydrogen bonds.