In biochemistry, intercalation (from Latin intercalare = to insert) is a special interaction between small molecules and the DNA. The small molecule is pushed into the space between two adjacent base pairs of the DNA double helix. As a result, the geometry of the DNA strand is distorted at these points (see figure). This disturbs transcription and consequently also replication. The intercalation for the chemotherapeutic effect of antibiotics or cytostatic drugs such as actinomycin or anthracyclines (e.g. doxorubicin, daunorubicin) is attributed to this effect.