Understanding the molecular mechanisms of how genetic information is copied.
DNA replication is a semiconservative process. Each original (template) strand of the double helix serves as a template for a new complementary strand. The resulting DNA molecules contain one original strand and one newly synthesized strand.
Multiple enzymes coordinate to ensure accurate and efficient replication.
DNA polymerase can only add nucleotides to the 3' end of a primer. Therefore, replication proceeds in a $5' \rightarrow 3'$ direction.
Taq polymerase is used to artificially replicate DNA because it can withstand high temperatures ($95^\circ\text{C}$) used to separate DNA strands in vitro.
The backbone of DNA consists of alternating phosphate and deoxyribose sugar groups (C₅H₁₀O₄). The nitrogenous bases (A, T, C, G) bond via hydrogen bonds:
Example: H₂O is needed for condensation reactions joining nucleotides, forming phosphodiester bonds.
Because each newly synthesized double-stranded DNA molecule contains one original (conserved) strand and one newly synthesized strand.
DNA ligase joins the Okazaki fragments on the lagging strand by creating phosphodiester bonds between them, sealing the nicks in the sugar-phosphate backbone.
Because DNA polymerase III can only synthesize in the $5' \rightarrow 3'$ direction. As the replication fork opens, the lagging strand template runs in the $3' \rightarrow 5'$ direction relative to the fork's movement, forcing polymerase to synthesize short fragments backwards.