Question

why does DNA when denatured not refold to its dsDNA form ?

Answer 1

Answer: Denaturation is the process in which the bio-molecules (especially nucleic acid, protein) in the presence some external factors (high salt concentration, pH, strong acid and base, heat or organic solvent like alcohol, chloroform etc.) losses its higher structure (quaternary, tertiary and secondary) and converted into their lowest state of structure (primary/native state). The dsDNA consist of chains of two nucleotides one nucleotide of one chain interact with one nucleotide of other chains, resultant the two single strands of nucleotide converted into a single double strand of DNA (dsDNA). The bond formed between the nucleotide is either double (A=T) or triple (G≡C) hydrogen bonds. In the presence of any external factors mentioned above these bonds are break and the double-stranded of DNA converted into two single strands of DNA (ssDNA). If external factor are consistent then there is no chance for renaturation (or formation of dsDNA)) from these two single strands of DNA. However, if we can remove the external denaturating factor and induce the renaturation factor then there is the chance for renaturation of DNA takes place. Like if denaturation takes place due to heat then the presence of that heat there is no chance for renaturation. However, if we remove the heat and cool the denatured solution of DNA then renaturation takes place and two single strands of DNA are converted into one double strand of DNA.