Molecular biology: A brief overview

Transcription and translation of the genetic code. The three major processes involved in the transmission of genetic information are: A, DNA replication, which involves the synthesis of a complementary strand of an original DNA template; B, DNA transcription, in which a complementary mRNA strand is synthesized from an original DNA template; and C, translation of mRNA, resulting in protein synthesis. Each process is represented in this figure, with the commonly used molecular biology techniques applied to study these processes.

The cell cycle. The four basic phases of the eukaryotic cell cycle are shown. The G₁ phase involves most protein biosynthesis. The S-phase entails most of the cell's DNA synthesis and some additional protein synthesis. The G₂ phase is characterized by the protein synthesis necessary for mitosis. In the M phase, the chromosomes condense and cell replication (mitosis) is initiated.

Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay. DNA strand breaks with exposed carboxy (-OH) termini are labeled, conjugated, and studied to determine in vitro pre-programmed cell death or apoptosis.

Western immunoblot analysis. Cell lysates are subjected to electrophoresis, transferred to a nitrocellulose membrane, incubated with protein-specific primary and marker-labeled (conjugated) secondary antibodies, and subsequently detected by means of chemiluminescence and x-ray film development.

Enzyme-linked immunosorbent assay (ELISA). Immobilized antigens are incubated with protein-specific primary antibodies and marker-labeled (conjugated) secondary antibodies. Protein complexes are then quantified by means of colorimetric assay.