概述了基因工程

Frederick Griffith's 1928 experiments with bacteria suggested a transforming principle. Oswald Avery, Colin Macleod, and Maclyn McCarty identified DNA as responsible for transformation in 1944. Alfred Hershey and Martha Chase confirmed in 1952 that viral DNA, not protein, transmits genetic information during bacterial infection using radioactively labeled bacteriophage.

Restriction enzymes cut DNA at specific sequences, breaking it into fragments. DNA ligases then join these fragments in desired orders to create new plasmids. This restriction enzyme-based cloning method was foundational for generating genetic constructs before newer techniques like recombineering and gene targeting emerged.

Transformation and transfection use divalent cations like calcium to increase cell membrane permeability for naked DNA uptake. Electroporation applies electric fields for the same purpose. Lipid nanoparticles surround DNA and fuse with membranes, while transduction uses viral vectors like lentiviruses to transfer genetic material into cells.

Homologous recombination allows integration into specific genomic sites by matching DNA sequences, enabling precise gene targeting. Genome editing uses custom-designed nucleases to generate double-strand breaks at specific loci, greatly improving targeting efficiency. Both techniques minimize off-target effects compared to random DNA integration.

Transgenic mice contain inserted foreign genes, like SV40 viral DNA, and can pass these genes to offspring. Knockout mice have specific genes rendered nonfunctional through homologous recombination. Rudolf Jaenisch created the first transgenic mouse in 1973, while Mario Capecchi and Oliver Smithies generated the first knockout mouse in 1989.

Researchers target cancer cells that over-express surface receptors using adenoviral vectors. In bladder cancer models, topical delivery of the vector to cancer cells enables successful gene transfer. Luciferase reporter genes confirm successful delivery, demonstrating how gene therapy can target specific cancer cell populations for therapeutic intervention.

Simple traits like herbicide resistance are achievable, but complex problems such as stress tolerance require modifying multiple pathways simultaneously. Safe and efficient delivery of genetic constructs to target cells remains challenging. Additionally, minimizing off-target effects and ensuring long-term stability of modifications are critical considerations for successful agricultural applications.