The secondary structure of DNA is formed by the complementary bonds between the nucleobases that make up the nucleotides. Replacing even one nucleotide in DNA can lead to the fact that the cell will begin to produce a protein in which one of the amino acids will be replaced by another. If this amino acid is crucial for a key role, for example, it enters the active center of the enzyme, the work of the protein will be significantly impaired. Specify the nucleobase, complimentary to guanine: