DNA and RNA are both nucleic acids. Deoxyribonucleic acid or DNA is made of nucleotides which are combined with covalent bonds and form a double chain. Nucleotides consist of deoxyribose, the phosphate group, and a nitrogenous base (adenine, cytosine, thymine, and guanine). Ribonucleic acid (RNA) also consists of nucleotides that are bound with covalent bonds, but this type of nucleic acid has one strand. Its nucleotides are made of ribose, the phosphate group, and a nitrogenous base (adenine, cytosine, uracil, and guanine).

The function of RNA is in synthesizing proteins. We differ three types of this molecule:
1. Messenger RNA
2. Ribosomal RNA
3. Transfer RNA
During transcription, an enzyme known as RNA polymerase binds to promoters of the DNA. Promoters are specific sequences of nucleotides that are present in many locations in the DNA molecule. They represent the starting point for transcription. RNA polymerase then breaks down hydrogen bonds between two strands of the DNA and attaches on one of them. A DNA strand is used as a template for new RNA molecule. In this way, pre-mRNA is made, which becomes mRNA after the introns are removed.

During transcription, an enzyme known as RNA polymerase binds to promoters of the DNA, which are specific sequences of nucleotides that are present in many locations in the DNA molecule. They represent the starting point for transcription. RNA polymerase then breaks down hydrogen bonds between two strands of the DNA and attaches on one of them. A DNA strand is used as a template for a new RNA molecule. In this way, pre-mRNA is made, which becomes mRNA after the introns are removed. A mRNA molecule enters the ribosomes, where transfer RNA attaches to it. A mRNA molecule is built of codons, which are sequences of three nucleotides in a row, which determinate an amino acid. The starting point in the translation process is AUG codon. Based on these codons, tRNA with adequate anticodons adds amino acids in order to make polypeptide molecules. The translation process is completed when the stop codon is reached.

Promoters are specific sequences of nucleotides that are present in many locations in the DNA molecule. They represent the starting point, from which a certain gene is being transcripted. Common promoter sequence in the DNA of eukaryotic cells is known as the TATA box because it consists of thymine and adenosine.

In the transcription process of a certain gene in the DNA molecule, hundreds of mRNA can be made. That is very important because in this way a specific protein can be produced continuously, rather than once.