Replication (school)

DNA copies before mitosis/meiosis (S phase). Semiconservative: each new helix keeps one old strand (Meselson-Stahl named). Helicase named: unwind. DNA polymerase named: add nucleotides 5' to 3'. Leading strand continuous; lagging Okazaki fragments named. Primer (RNA) named. Proofreading named as a reason errors are rare. These notes do not teach PCR as a lab method beyond the word if the book uses it. Semiconservative replication ensures each new cell gets a complete accurate copy of the genome. The Meselson-Stahl experiment confirmed this model using heavy isotope labelling.

REPLICATION (SCHOOL) is an independent FBISE learning unit because students must connect its structures and processes with their biological functions and examples.

WHY SEMI: Old strand is the template. Daughter helix: one old, one new. Conservative and dispersive were rejected by the density experiment (school). Meselson-Stahl (1958): heavy ¹⁵N labelled DNA → mixed density after one generation → light after two. Proves each new helix retains one parental strand. Examples: S phase; Two identical helices (ignore mutation); Origins of replication named. ENZYME NAMES: Helicase, polymerase, ligase (joins fragments). No kit list, no temperatures as a protocol. PCR is a named lab idea in some books — word only. Helicase unwinds. Primase makes RNA primer. DNA polymerase adds nucleotides. Ligase joins Okazaki fragments. All names for exams — no PCR temperature protocol. Examples: Leading vs lagging; Ligase seals; No PCR recipe. Exam semiconservative: Helix opens. Each strand templates a new strand. Each daughter DNA has one parental strand.