This lesson will describe the definition and structure of thymine as it relates to the formation of DNA. Also, there will be a small discussion about key facts that separate thymine from the other bases used to form the DNA helix.
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 are attracted to one another and form specific partnerships to help in the creation of DNA. DNA is a small molecule found in every cell of your body and is responsible for writing your body’s genetic information.DNA is best visualized by picturing a long, twisted, spiraling ladder. The inner portion of the ladder is constructed of rungs.
If you picture the four bases of DNA as rungs that assist with the formation of the ladder, you can get a solid understanding of how the bases hold the DNA structure together. Just as the rungs have a responsibility to stabilize the ladder, the bases have a responsibility to stabilize the structure of DNA.Thymine is an interesting base because it is the only one of the four bases found exclusively inside of DNA. The other bases are also found in RNA, which is often thought of DNA’s cousin because of the close relationship and joint assistance the two often share genetic information transfer process.
Structure of Thymine
Thymine is constructed of one type of specific nitrogenous base that serves as its basic foundation. 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 one phosphate group and one deoxyribose sugar molecule to complete its signature recipe.Thymine is most often represented as a ring-like structure called a pyrimidine. Each respective base is in the shape of a ring-like form and there are two types.
A purine is a base that contains a double ring form. By contrast, a pyrimidine is a base that contains a single ring form. Adenine and guanine are the purines. Thymine and cytosine are the pyrimidines. Adenine and thymine are almost always going to be partners on the DNA ladder. Cytosine and guanine form the other base pair partnership. The easiest way to remember the partnership is by their respective acronyms: A-T and C-G.
This partnership is important because, if not paired correctly, the entire DNA structure will be unstable, causing significant problems down the road.
What Makes Thymine Different?
As mentioned in earlier, thymine is the only base found exclusively in DNA. This is because it serves as the main stabilizer. When the rungs of the DNA ladder are being created, each base is searching for its partner.
Ever heard the phrase ‘opposites attract’? Well, in this case it’s the truth. Because the bases are opposites (two are purines and two are pyrimidines) the purine bases want to bind with the pyrimidine bases. Therefore, thymine, a pyrimidine, will bind to adenine, a purine. When this occurs, there are two hydrogen bonds formed to completely stabilize the piece of the DNA ladder. If thymine was to bond with any other of the bases, this particular hydrogen bond wouldn’t be formed correctly and the DNA ladder would have rungs crossing one another. This would cause the ladder to bow in and out and would be ineffective for further use by the body.
How Thymine Could Be a Problem
Of course, everything comes with a potential problem, and thymine is no exception.
From time to time, there will be an inadvertent mutation, or a strangely formed DNA structure. This usually happens because thymine is not performing its duty as the stabilizer and, as a result, your body creates something called a thymine dimer. A thymine dimer is another term for the end product created by a natural mutation in a small piece of your body’s DNA combined with exposure to increased amounts of ultraviolet light.
Many times this can happen when you perform activities such as frequent sunbathing without sunscreen protection. When such an occurrence happens, there will be a kink in that entire piece of DNA, meaning it cannot function normally.If this occurs now and again, it isn’t necessarily a problem, because your body has the ability to rid itself of toxic chemicals and similar problems on a small level.
However, if these thymine dimers are continually formed and your body is unable to clear them out because they begin to replicate, you could eventually have a condition known as melanoma. Melanoma is a dangerous form of skin cancer that affects many individuals every year and often starts out by something as simple as an oddly shaped or strange looking mole.
As you can see, thymine plays a significant role in your body. As it not only is necessary for the correct formation of the DNA ladder, but also serves as the main stabilizer to ensure that this ladder will have a solid foundation, so your body can acquire the genetic information needed for each of its cells. Also, you can see the negative potential of thymine if exposed to excess amounts of UV light, such as frequent overexposure to the sun.