Thymine: Definition, Mutation, Structure, Properties and Bases

It is one of the four nitrogenous nucleobases that form the basic components of deoxyribonucleic acid (DNA).

Also known as 5-methyluracil, thymine (T) is a pyrimidine nucleobase , which combines with adenine (A), a purine nucleobase.

They bind to each other as a pair of bases through two hydrogen bonds, which stabilize the nucleic acid structures in the DNA. When stacked with the other pair of bases, guanine (G) and cytosine (C), the helical structure of DNA (or RNA) is formed.

In the structure of RNA, thymine is replaced by the nucleobase of uracil. As its alternative name suggests (5-methyluracil), thymine can be derived by methylation of uracil in the 5th carbon (a branching of methyl-CH3 is added to the pyrimidine ring).

The combination of thymine, with the pentose sugar and deoxyribose forms the nucleoside deoxythymidine (alternatively called “thymidine”). A nucleoside is a nucleotide without a phosphate group.

Mutation and Cancer

When exposed to ultraviolet radiation, such as sunlight, covalent bonds are formed between adjacent thymine molecules in the same DNA chain, creating thymine dimers. This process causes damage, causing the DNA to form “folds.” This inhibits the normal function of DNA, which can not be replicated or transcribed.

Fortunately, most cells can repair damaged DNA. This can be achieved in two ways: repair enzymes called fotoliase can break the covalent bond, using light as an energy source for cleavage of the bond.

This process is called photoreactivation and is possible in most organisms, although not in placental mammals.

The second mechanism involves a cleavage enzyme, which removes the damaged section of a single strand of DNA. The excised nucleotides are replaced by DNA polymerase and a final phosphodiester bond (the stabilizing structure of the nucleic acids) is formed by the DNA ligase.

Structure of thymine

The formula of timina is C5H6N2O2.

Thymine is constructed from a specific type of nitrogenous base that serves as the basic base. Think of this as the secret ingredient for a particular recipe. For example, thymine would have a different nitrogenous base than adenine.

In addition to this, it also contains a phosphate group and a deoxyribose sugar molecule to complete your recipe.

Properties

It is a heterocyclic, aromatic and organic compound. Heterocyclic compounds or “ring structures” are cyclic compounds (the atoms in the compound are connected to form a ring), which have atoms of at least two different elements.

An “organic” compound contains carbon, so a heterocyclic organic compound contains carbon atoms and one or more additional elements such as sulfur, nitrogen or oxygen.

The term aromatic describes a molecule that is cyclic and flat, with a ring of resonance bonds, which give stability to the molecule. This means that it does not break or react with other substances easily.

The four DNA bases

There are four bases that support the formation of DNA. They are thymine, adenine, guanine and cytosine and are also known by the acronyms T, A, G and C. These bases attract each other and form specific associations to help the creation of DNA.

DNA is a small molecule that is found in every cell of your body and is responsible for writing the genetic information of your body.

DNA is best visualized when imagining a long, twisted and spiral staircase. The internal part of the staircase is built with steps. If you visualize the four bases of DNA as rungs that help with the formation of the ladder, you can gain a solid understanding of how the bases hold the DNA structure together .

In the same way that the steps have the responsibility to stabilize the ladder, the bases have the responsibility to stabilize the structure of the DNA.

Thymine is an interesting base because it is the only one of the four bases found exclusively within DNA.

The other bases are also found in RNA, which is often thought to be the cousin of DNA because of the close relationship and the joint assistance. Often, the two share the process of transferring genetic information.