The key difference between Watson and Crick and Hoogsteen base pairing is that Watson and Crick’s base pairing is the standard way that describes the formation of base pairs between purines and pyrimidines. Meanwhile, Hoogsteen base pairing is an alternative way of forming base pairs in which the purine takes a different conformation with respect to pyrimidine.
A nucleotide has three components: a nitrogenous base, a pentose sugar and a phosphate group. There are five different nitrogenous bases and two pentose sugars involved in the structure of DNA and RNA. When these nucleotides form a nucleotide sequence, complementary bases, either purines or pyrimidines, form hydrogen bonds between them. This is known as base pairing. Therefore, a base pair is formed by joining two nitrogenous bases by hydrogen bonds. Watson and Crick’s base pairing is the classic or standard approach, while Hoogsteen base pairing is an alternative way of forming base pairs.
CONTENTS
1. Overview and Key Difference
2. What is Watson and Crick Base Pairing
3. What is Hoogsteen Base Pairing
4. Similarities Between Watson and Crick and Hoogsteen Base Pairing
5. Side by Side Comparison – Watson and Crick vs Hoogsteen Base Pairing in Tabular Form
6. Summary
What is Watson and Crick Base Pairing?
Watson and Crick’s base pairing is the standard method that explains the base pairing of nitrogenous bases in nucleotides. James Watson and Francis Crick, in 1953, explained this base paring method, which stabilizes the double standard helices of DNA. According to Watson and Crick base pairing, adenine forms hydrogen bonds with thymine in DNA and with uracil in RNA. Moreover, guanine forms hydrogen bonds with cytosine in both DNA and RNA.
Figure 01: Watson and Crick Base Pairing
There are three hydrogen bonds between G and C while there are two hydrogen bonds between A and T. These base pairs allow the DNA helix to maintain its regular helical structure. Most nucleotide sequences (60%) have Watson and Crick base pairs which are stable at neutral pH.
What is Hoogsteen Base Pairing?
Hoogsteen base pairing is an alternative way of forming base pairs in nucleic acids. This was first described by American biochemist Karst Hoogsteen in 1963. Hoogsteen base pairs are similar to Watson and Crick base pairs. They occur between adenine (A) and thymine (T), and guanine (G) and cytosine (C). But purine takes a different conformation with respect to pyrimidine. In A and T base pair, the adenine is rotated in 1800 about the glycosidic bond, allowing an alternative hydrogen bonding scheme. Similarly, in G and C pair, guanine is rotated 180° about the glycosidic bond. Moreover, the angle of glycosidic bonds is larger in Hoogsteen base pairs. Besides, the formation of Hoogsteen base pairs is not stable at neutral pH.
Figure 02: Watson and Crick Base Pairing vs Hoogsteen Base Pairing
Hoogsteen base pairs are non-canonical base pairs which make the nucleotide sequences less stable than the standard base pairing. Moreover, they can result in the disruption of DNA double helix. Though Hoogsteen base pairs occur naturally, they are very rare.
What are the Similarities Between Watson and Crick and Hoogsteen Base Pairing?
- Watson and Crick and Hoogsteen base pairing are two ways to describe the formation of base pairs in nucleic acids.
- Both occur naturally in DNA.
- Moreover, they exist in equilibrium with one another.
- Base pairs are similar in both methods.
What is the Difference Between Watson and Crick and Hoogsteen Base Pairing?
Watson and Crick base pairing is the standard way that describes the formation of base pairs between purines and pyrimidines. On the other hand, Hoogsteen base pairing is an alternative way of forming base pairs in which the purine takes a different conformation with respect to pyrimidine. So, this is the key difference between Watson and Crick and Hoogsteen base pairing. Watson and Crick base pairing was described by James Watson and Francis Crick in 1953 while Hoogsteen base pairing was described by Karst Hoogsteen in 1963. Moreover, Watson and Crick base pairs are stable while Hoogsteen base pairs are typically less stable.
The below infographic summarizes the difference between Watson and Crick and Hoogsteen base pairing.
Summary – Watson and Crick vs Hoogsteen Base Pairing
Watson and Crick base pairing and Hoogsteen base pairing are two types of ways that describe the formation of nitrogenous bases in nucleotide sequences. In Hoogsteen base pairing, the purine base takes a different conformation with respect to pyrimidine base. So, this is the key difference between Watson and Crick and Hoogsteen base pairing. Moreover, Watson and Crick base pairs stabilize the DNA double helix while Hoogsteen base pairs make the helix unstable. However, both types of base pairs occur naturally, and they exist in equilibrium with one another.