Biotechnology tools let scientists read, copy, move, and edit DNA so they can study genes and change biological systems in controlled ways. These tools matter in medicine, agriculture, forensics, and basic research because DNA information is central to inheritance and cell function. A typical biotechnology workflow starts with a DNA sample and uses several methods in sequence to answer a specific question or build a desired genetic change.
Key Facts
- PCR copies a target DNA region using cycles of denaturation, primer annealing, and extension.
- One ideal PCR cycle doubles the target DNA amount, so after n cycles there are about 2^n copies.
- Gel electrophoresis separates DNA fragments mainly by size, with smaller fragments moving farther through the gel.
- DNA cloning often uses restriction enzymes and DNA ligase to insert a DNA fragment into a plasmid vector.
- DNA sequencing determines the order of bases in DNA, written using A, T, C, and G.
- CRISPR-Cas9 uses a guide RNA to direct Cas9 to a matching DNA sequence, where Cas9 cuts the DNA.
Vocabulary
- PCR
- Polymerase chain reaction is a method that makes many copies of a chosen DNA sequence.
- Gel electrophoresis
- Gel electrophoresis is a technique that separates DNA fragments by pulling them through a gel with an electric field.
- Plasmid
- A plasmid is a small circular DNA molecule often used as a vector to carry inserted genes into cells.
- DNA sequencing
- DNA sequencing is the process of determining the exact order of nucleotides in a DNA molecule.
- CRISPR-Cas9
- CRISPR-Cas9 is a genome editing system that uses a guide RNA and the Cas9 protein to cut a specific DNA sequence.
Common Mistakes to Avoid
- Confusing PCR with cloning is wrong because PCR copies DNA in a tube, while cloning places DNA into a vector and often into living cells.
- Assuming larger DNA fragments move farther on a gel is wrong because larger fragments travel more slowly through the gel matrix.
- Forgetting that primers define the PCR target is wrong because DNA polymerase can only extend from primers bound to specific sequences.
- Thinking CRISPR automatically inserts the exact desired change is wrong because Cas9 makes a cut, and the cell's repair process determines the final DNA outcome.
Practice Questions
- 1 A PCR reaction starts with 5 copies of a target DNA fragment. If amplification is perfectly efficient, how many target copies are present after 10 cycles?
- 2 A gel has DNA fragments of 200 bp, 800 bp, and 1500 bp loaded into one lane. List the fragments from farthest traveled to least far traveled.
- 3 A researcher wants to edit a gene and then confirm that the edit happened. Explain how PCR, gel electrophoresis, and DNA sequencing could each be used in this workflow.