01Core tools
Gel electrophoresis separates DNA by size: DNA is negative, so it runs toward the positive electrode; smaller fragments travel farther.
PCR amplifies DNA: denature (~95 °C), anneal primers (~55 °C), extend with heat-stable Taq polymerase (~72 °C). Each cycle doubles DNA: 2ⁿ copies.
Bacterial transformation: insert a gene into a plasmid with restriction enzymes and ligase, then get bacteria to take it up (selection with antibiotic resistance).
02Applications
DNA sequencing reads bases; used in medicine and phylogeny. CRISPR-Cas9 edits genes precisely. Biotech produces insulin, GMO crops, forensic DNA fingerprints and gene therapy.
03Notebook box
Gel rule: DNA runs to red (positive). Small = far.
Worked example: After 10 PCR cycles from 1 DNA molecule, how many copies? → 2¹⁰ = 1,024.