DNA can be denatured at high temperatures or in alkaline solutions. But DNA can be annealed at low temperatures. I want to ask, could it be annealed in acidic medium?


1 Answer 1


Hello and welcome Nandini Yadav,

It is worth mentioning DNA is an acid (Deoxyribonucleic acid) and intracellular pH is most commonly between 7.0 and 7.4.

Alkaline reagent Example

"The sodium hydroxide (NaOH) is a commonly used reagent to denature the DNA by increasing the pH. At an alkaline pH, OH- groups are predominant. They remove the hydrogen- bonds-contributing protons from guanine and thymine, thus breaking the hydrogen bonds between the two oligonucleotides."


You can see in the image below hydrogen bonds between nucleotides Adenine (A), Cytosine (C), Guanine (G) and Thymine (T).

DNA Bonds

Acid reagent Example

A decrease in the pH was found to deteriorate the thermal stability of DNA


At an acidic pH, the H+ in the surrounding environment of DNA is high and therefore the hydrogen bonds between Adenine (A) and Thymine (T), Cytosine (C) - Guanine (G) will 'break'.

More information here.


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