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Biotechnology & Genetic Engineering Cheat Sheet
A printable reference covering restriction enzymes, recombinant DNA, PCR, gel electrophoresis, CRISPR-Cas9, cloning, and ethical considerations for grades 11-12.
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Biotechnology uses living systems, cells, and biological molecules to solve problems in medicine, agriculture, research, and industry. Genetic engineering is the direct modification of DNA to add, remove, or change genes. Students need this cheat sheet to connect lab techniques with the molecular biology behind them. It helps organize the major tools used to copy, cut, separate, transfer, and edit DNA. The core ideas include recombinant DNA, PCR amplification, gel electrophoresis, DNA sequencing, cloning, and CRISPR-Cas9 gene editing. Restriction enzymes cut DNA at specific sequences, while DNA ligase joins DNA fragments together. PCR makes many copies of a target DNA segment using cycles of denaturation, annealing, and extension. Ethical thinking is also essential because genetic technologies can affect health, ecosystems, privacy, and future generations.
Key Facts
- Restriction enzymes cut DNA at specific recognition sequences, often leaving sticky ends that can base pair with matching DNA fragments.
- DNA ligase forms phosphodiester bonds between DNA fragments, sealing the sugar phosphate backbone in recombinant DNA.
- PCR copy number can be estimated with final copies = initial copies x 2^n, where n is the number of PCR cycles.
- PCR has three main steps: denaturation separates DNA strands, annealing lets primers bind, and extension lets DNA polymerase build new strands.
- In gel electrophoresis, DNA moves from the negative electrode to the positive electrode because DNA has a negatively charged phosphate backbone.
- Smaller DNA fragments travel farther through an agarose gel than larger DNA fragments over the same time.
- Transformation efficiency can be calculated as transformation efficiency = number of colonies / micrograms of plasmid DNA used.
- CRISPR-Cas9 uses a guide RNA to target a DNA sequence, and Cas9 cuts the DNA so the cell can repair or alter the gene.
Vocabulary
- Recombinant DNA
- DNA made by joining genetic material from two or more sources into one molecule.
- Restriction enzyme
- A bacterial enzyme that cuts DNA at a specific nucleotide sequence.
- Plasmid
- A small circular DNA molecule, often found in bacteria, that can be used as a vector to carry foreign DNA.
- PCR
- Polymerase chain reaction, a technique used to make many copies of a specific DNA segment.
- Gel electrophoresis
- A lab method that separates DNA fragments by size using an electric field and a gel matrix.
- CRISPR-Cas9
- A gene editing system that uses guide RNA and the Cas9 enzyme to cut DNA at a chosen sequence.
Common Mistakes to Avoid
- Thinking PCR copies an entire genome, which is wrong because PCR amplifies only the DNA region targeted by the primers.
- Forgetting that DNA runs toward the positive electrode, which is wrong because the negatively charged phosphate backbone is attracted to positive charge.
- Assuming larger DNA fragments move farther in a gel, which is wrong because larger fragments are slowed more by the gel matrix.
- Using the wrong restriction enzyme for a plasmid and insert, which is wrong because incompatible cut ends may not base pair or ligate correctly.
- Treating CRISPR as perfectly precise, which is wrong because guide RNA can sometimes bind similar off-target sequences.
Practice Questions
- 1 A PCR reaction begins with 20 copies of a DNA target. How many copies are expected after 10 cycles if amplification is ideal?
- 2 A transformation plate has 240 colonies, and the bacteria received 0.08 micrograms of plasmid DNA. What is the transformation efficiency?
- 3 In a gel electrophoresis result, fragments of 500 bp, 1,500 bp, and 4,000 bp are loaded in the same lane. Which fragment should travel farthest from the wells?
- 4 Why must scientists consider ethics, safety, and consent when using genetic engineering in humans?