Guanine is found in DNA.
Nucleotides are complex molecules that are the building blocks of deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Each nucleotide has three parts – a five-carbon sugar, a phosphate group, and an organic base. There are two variations of the sugar, depending on whether the nucleotide is in a DNA or RNA molecule. In addition, one of five different organic bases can be attached to each nucleotide – adenine, cytosine, guanine, thymine or uracil. Cytosine, guanine and adenine are found in RNA and DNA molecules, while thymine is only in DNA and uracil is only in RNA.
Three hydrogen bonds link guanine and cytosine in DNA.
All five bases have a complex ring structure made up of carbon and nitrogen atoms. Due to the nitrogen atoms found in the ring, the bases are also called nitrogenous bases. Each of the bases has a different chemical structure from the other four, which allows for specific base pairing between each of the bases.
The five bases can be divided into two groups based on the number of rings found in their chemical structure. Purine bases are composed of two rings of atoms and pyrimidine bases have only one ring of atoms. Purine bases include adenine and guanine, while pyrimidine bases are cytosine, thymine and uracil. When the bases pair and bond, the purine bases only bond to the pyrimidine bases. More specifically, adenine only binds thymine or uracil and cytosine only binds guanine.
Guanine is one of the four bases that make up RNA.
This specific base pair is very important for the stability of a DNA molecule, which is made up of two strands of nucleotides that coil together to form a double helix. The two strands are held together by hydrogen bonds between complementary bases on each strand. Adenine and thymine are joined by two hydrogen bonds, while guanine and cytosine are joined by three hydrogen bonds. Only these pairs are able to form the hydrogen bonds necessary to make the DNA molecule stable.
Due to the binding that occurs only between the purine bases and the pyrimidine bases, the distance between the two strands remains uniform, adding more stability to the DNA molecule. When a purine base bonds with a pyrimidine base, a double-ring molecule bonds with a single-ring molecule. If a purine base attached to a purine base, then two double-ring molecules would be attached, or if a pyrimidine base were attached to a pyrimidine base, then two single-ring molecules would attach. If all these binding scenarios took place, the DNA molecule would bend in and out and not be uniform, which would affect its overall structure and stability. Having a stable DNA molecule is critical to success as it carries the genetic information of each organism.