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Difference Between Denaturation And Renaturation Of DNA

Difference Between Denaturation And Renaturation Of DNA

DNA is responsible for carrying our genetic information and the functioning of our organs. Denaturation and Renaturation of DNA refer to the processes that help in the study of genetic information. These methods basically help to unwind and rewind the double-strand DNA by heating and cooling, respectively.

Table of Contents:

  • What is Denaturation?
  • Methods of Denaturation
  • Effect of Denaturation of DNA
  • What is Renaturation?
  • Difference Between Denaturation and Renaturation of DNA
  • Practice Problems
  • Frequently Asked Questions

What is Denaturation?

We all know that DNA is a double-stranded helical structure. Denaturation is a process that includes the unwinding of two strands under high temperature, pH, etc., which results in two separate single strands of DNA. Certain factors affect the stability of the DNA structure. The hydrogen bonds between the double-stranded DNA are broken to get two separate strands. However, the covalent bonds of DNA remain the same.

Methods of Denaturation

There are various methods involved in the Denaturation process. They are given below:

  • Thermal Denaturation

Generally, Denaturation is done by heating at a temperature >80-90℃. Critical temperature refers to the temperature at which DNA is half-denatured. It is also called the (Tm)melting temperature. This melting temperature varies and depends on the composition and length of the DNA bases. 

  • Extreme pH

The hydrogen bonds between the two strands of the DNA are dissociated at high pH of >11.3. This is due to the presence of generous OH- ions. This extreme pH results in the Denaturation of DNA.

  • Denaturing Agents

Hydrogen bonds can be destabilised by lowering the salt concentration. For example, urea and formaldehyde can form hydrogen bonds with nitrogen bases. Aldehydes break the hydrogen bonding between the strands by modifying the electronegative centres of nitrogenous bases.

Effect of Denaturation of DNA

  • The rate of absorption is directly proportional to the rate of denaturation. So the absorption of UV light increased at 260 nm wavelength.
  • Physical change in the structure of DNA due to the decrease in viscosity.

What is Renaturation?

Renaturation is a process of reversal of denaturation. It includes the rewinding of separate single strands of DNA. It is also known as annealing. The unwound strand of DNA returns back to the normal DNA structure or rewind by bringing the temperature and pH to the optimum biological level.

Renaturation can be done fast by a one-step process in case the DNA is not completely denatured. If the DNA is completely denatured, renaturation involves a two-step process. Initially, the complementary strands join together by random collision and form a double helix structure by rewinding. 

  • The denatured DNA is cooled under suitable conditions for renaturation. Renaturation depends on temperature, pH, length and constituents of the DNA structure. 
  • The renaturation rate of DNA is directly proportional to the number of complementary sequences present.
  • The absorption of UV light decreased at 260 nm wavelength due to the increase in viscosity.

Difference Between Denaturation and Renaturation of DNA

Denaturation and Renaturation of DNA help in determining the size and composition of the genome. It is used to understand the relationship between two genomes and the sequence of repetition in the present genome. The table below shows the difference between Denaturation and Renaturation of DNA:

Denaturation of DNA

Renaturation of DNA

Double-strand DNA is separated into two single strands.

Denatured single strands of DNA are combined to form double strands.

Heating is involved.

Cooling is involved.

DNA is unwinded.

DNA is rewinded.

Breaking of hydrogen bonds between two DNA strands.

Formation of hydrogen bonds between two DNA strands.

Absorption of UV light increases

Absorption of UV light decreases

Increase in viscosity

Decrease in viscosity

Practice Problems

Q1. Which of the following causes a physical change in the structure of DNA?

A. Decrease in viscosity
B. Increase in viscosity
C. No Change in viscosity
D. None of the above

Answer: A. Decrease in viscosity

Explanation: Physical change in the structure of DNA due to the decrease in viscosity.

Q2. Which of the following is involved in the Renaturation process?

A. Heating
B. Cooling
C. Melting
D. Freezing

Answer: B. Cooling

Explanation: The unwound strand of DNA returns back to the normal DNA structure or rewind, by bringing the temperature and pH to the optimum biological level. The denatured DNA is cooled under suitable conditions for renaturation. 

Q3. Which of the following break the hydrogen bonding between the two DNA strands?

A. Alcohol
B. Benzoyl
C. Aldehydes 
D. None of the above

Answer: C. Aldehydes 

Explanation: Aldehydes break the hydrogen bonding between the strands by modifying the electronegative centres of nitrogenous bases.

Frequently Asked Questions

Q1. What is the full form of DNA?
Answer: DNA full form is Deoxyribonucleic Acid. It refers to the molecules that transmit and carry the genetic information from parents to children.

Q2. What are the different types of DNA?
Answer: There are various types of DNA, namely, A-DNA, B-DNA and Z-DNA. They are double helix, right-handed helix and zig-zag double helix in shape, respectively.

Q3. When does Renaturation occur?
Answer: Renaturation occurs when the denatured DNA is cooled under specific conditions.

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