Difference between Cytosine and Thymine - Testbook.com
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The Basics of Cytosine
Cytosine is a type of pyrimidine that carries a heterocyclic aromatic ring. It is a component of both DNA and RNA, where it pairs with another base known as guanine, a process referred to as complementary base pairing.
Cytosine features an amine group at the C4 position and a keto group at the C2 position.
Getting to Know Thymine
Thymine is a pyrimidine base that is exclusively found in DNA. In RNA, thymine is replaced by a base called uracil. Thymidine, or deoxythymidine, is a nucleoside molecule formed by the combination of thymine and deoxyribose.
Thymine carries two keto groups at the C2 and C4 positions and a methyl group at the C5 position.
Comparing Cytosine and Thymine
Cytosine |
Thymine |
|
Chemical formula: C 4 H 5 N 3 O |
Chemical formula: C 5 H 6 N 2 O 2 |
|
A nitrogenous base present in both DNA and RNA. |
A nitrogenous base only present in DNA. |
|
Complementary base pair is guanine. |
Complementary base pair is adenine. |
|
Cytosine and guanine are linked by three hydrogen bonds. |
Thymine and adenine are linked by two hydrogen bonds. |
|
Contains an amine group and a keto group. |
Contains two keto groups and a methyl group. |
Further Reading:
- Understanding Nucleotides
- Distinguishing Between Nucleotides and Nucleosides
- The Difference Between Purines and Pyrimidines
Continue exploring more interesting topics in Biology.
Frequently Asked Questions
What are nitrogenous bases?
Nucleobases or nitrogenous bases are the basic components that form nucleosides and nucleotides. A DNA molecule has four nitrogenous bases, namely – Adenine, Guanine, Cytosine and Thymine. At the same time, RNA has uracil instead of thymine. These bases are held together by hydrogen bonds.
What is complementary base pairing?
The lock and key pairing of nucleobases are called base pairing. It is always Adenine that pairs with Thymine or Uracil. Likewise, Cytosine pairs with Guanine. Various functions of the DNA are based on this complementary base pairing.
What are purines and pyrimidines?
The nitrogenous bases can be either purines or pyrimidines. Purines have a pyrimidine ring with an imidazole, whereas pyrimidines have two nitrogen atoms. Adenine and guanine are called purines. Cytosine, thymine and uracil are the pyrimidines.
What is cytidine?
Cytosine with a ribose ring (sugar structure) forms a nucleoside molecule. This nucleoside is called cytidine. Also, if the ribose ring is deoxyribose, it is called deoxycytidine.
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