Molecular Biology - Central Dogma & Protein Synthesis

The fundamental principle describing the flow of genetic information: DNA $\to$ RNA $\to$ Protein. It states that information cannot be transferred back from protein to nucleic acid, or from RNA to DNA (with exceptions like reverse transcription).

To produce two identical copies of a DNA molecule from a single original DNA molecule, ensuring that each daughter cell receives a complete set of genetic material during cell division.

Each new DNA molecule consists of one original (parental) strand and one newly synthesized (daughter) strand.

1. DNA Helicase: Unwinds the double helix by breaking hydrogen bonds between base pairs.
2. DNA Topoisomerase (e.g., Gyrase): Relieves supercoiling tension ahead of the replication fork.
3. Single-Strand Binding Proteins (SSBPs): Bind to and stabilize the separated single DNA strands, preventing them from re-annealing.

Synthesizes short RNA primers, which provide a free 3'-OH group that DNA polymerase can extend from, as DNA polymerase cannot initiate DNA synthesis de novo.

1. DNA Polymerase III: The primary enzyme for synthesizing new DNA strands during elongation, adding nucleotides in the 5' to 3' direction.
2. DNA Polymerase I: Removes RNA primers (5' to 3' exonuclease activity) and fills in the gaps with DNA (5' to 3' polymerase activity).

Short DNA segments synthesized discontinuously on the lagging strand during DNA replication. Because DNA polymerase can only synthesize in the 5' to 3' direction, the lagging strand must be synthesized in fragments as the replication fork opens. These fragments are later joined by DNA ligase.

Joins the Okazaki fragments on the lagging strand, and any other nicks in the DNA backbone, by forming phosphodiester bonds.