Question

In isolated DNA kept at $82-{90}^{o}C$

• A. The two strands uncoil and separate
• B. Fragmentation occurs
• C. Thymine is replaced by uracil
• D. The structure is stabilised

Answer 1

The correct option is A The two strands uncoil and separate

DNA has a double helix structure. The two strands of DNA run anti-parallel to each other in which adenine of one strand is attached to thymine of the opposite strand by two hydrogen bonds while three hydrogen bond exists between guanine and cytosine. On heating DNA at 82${}^o$C to 90${}^o$C, the hydrogen bond holding the two strands together breaks and the two strands of the DNA uncoils and separate.

So, the correct answer is option A.