What would happen if we place denatured DNA in acidic medium? 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?

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."

Source

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

Source

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.