The basics of molecular biology involve the replication of deoxyribonucleic acid and its transcription and translation into proteins. Biochemical assays such as the Southern blot analysis, polymerase chain reaction (PCR), Northern blot analysis, reverse-transcriptase PCR, microarray technology, Western blot analysis, immunohistochemistry, enzyme-linked immunosorbent assay, and flow cytometry utilize various aspects of molecular biology. To understand these assays requires some basic understanding of the principles of molecular biology. This paper provides basic information on the methodology and techniques used in these assays.