Rucete ✏ AP Biology In a Nutshell
16. Biotechnology
This chapter introduces key biotechnology techniques used in medicine, agriculture, and genetic research. It explains how DNA can be manipulated, amplified, separated, and edited using tools such as bacterial transformation, gel electrophoresis, PCR, and CRISPR-Cas9.
Bacterial Transformation
• Foreign DNA (usually a plasmid) is introduced into bacterial cells.
• Heat shock is used to create temporary pores for DNA entry.
• Selectable marker (like antibiotic resistance gene) allows transformed cells to be identified.
• Recombinant DNA: DNA from different sources combined using restriction enzymes and ligase.
• Transformed bacteria can produce useful products (e.g., insulin).
Gel Electrophoresis
• Separates DNA fragments by size and charge.
• DNA is cut by restriction enzymes → loaded into gel wells → electric current applied.
• DNA (negatively charged) moves toward the positive end.
• Smaller fragments travel farther than larger ones.
• DNA ladder (marker) helps estimate fragment size → creates DNA fingerprint.
Polymerase Chain Reaction (PCR)
• Amplifies specific DNA fragments exponentially.
• Three steps in each cycle:
1. Denaturation: heat separates DNA strands.
2. Annealing: primers bind to target DNA.
3. Extension: DNA polymerase adds nucleotides.
• After n cycles: 2ⁿ copies of DNA fragment are produced.
• Used in forensics, diagnostics, bioinformatics, evolutionary biology.
CRISPR-Cas9
• Natural bacterial immune system adapted for gene editing.
• Bacteria store viral DNA in CRISPR regions to recognize future infections.
• Cas9 enzyme uses guide RNA to cut DNA at specific locations.
• Two outcomes:
– Knockout: gene is disrupted → helps study gene function.
– Knock-in: donor DNA replaces original sequence via cell’s repair system.
In a Nutshell
Biotechnology allows scientists to manipulate DNA to explore gene function, diagnose diseases, and create genetically engineered organisms. Tools like bacterial transformation, gel electrophoresis, PCR, and CRISPR enable cloning, amplification, separation, and editing of DNA for research and practical applications.