1. Structure of DNA A, T, C, G

2. Adenine

3. Adenine is one of the two purine nucleobases (the other being guanine) used in forming nucleotides of the nucleic acids. nucleobasesguaninenucleotidesnucleic acids In DNA, adenine binds to thymine via two hydrogen bonds to assist in stabilizing the nucleic acid structures.thymine hydrogen bonds In RNA, which is used in the cytoplasm for protein synthesis, adenine binds to uracil.cytoplasm protein synthesisuracil

4. Thymine

5. One of the common mutations of DNA involves two adjacent thymines or cytosine, which, in presence of ultraviolet light, may form thymine dimers, causing "kinks" in the DNA molecule that inhibit normal function.ultraviolet lightthymine dimers

6. Cytosine

7. In DNA and RNA, cytosine is paired with guanine. guanine However, it is inherently unstable, and can change into uracil (spontaneous deamination). This can lead to a point mutation (example sickle-cell) if not repaired by the DNA repair enzymes such as uracil glycosylase, which cleaves a uracil in DNA.uracilspontaneous deaminationpoint mutationDNA repairenzymes

8. Guanine

9. The first isolation of guanine was reported in 1844 from the excreta of sea birds, known as guano, which was used as a source of fertilizer. About fifty years later, Fischer determined the structure and also showed that uric acid can be converted to guanine.