Genetic Engineering & Biotechnology
Recombinant DNA technology transfers a target gene from one organism into another using vectors or amplifies DNA fragments in vitro using the polymerase chain reaction (PCR). Because the genetic code is universal across nearly all living organisms, the transformed host cell can transcribe and translate the transferred DNA into a functional protein.
- Recombinant DNA
- DNA that has been formed artificially by combining constituents from different organisms.
- Reverse Transcriptase
- An enzyme that synthesizes DNA (cDNA) from an RNA template.
- DNA Ligase
- An enzyme that joins the sugar-phosphate backbones of two DNA fragments.
Mitosis (2n → 2n) vs Meiosis (2n → n) & Ribosome Protein Synthesis
Key Concepts & Exam Definitions (5)
- Recombinant DNA
- DNA that has been formed artificially by combining constituents from different organisms.
- Reverse Transcriptase
- An enzyme that synthesizes DNA (cDNA) from an RNA template.
- DNA Ligase
- An enzyme that joins the sugar-phosphate backbones of two DNA fragments.
- Gene Therapy
- The introduction of a normal allele into cells to replace a defective, disease-causing allele.
- DNA Probes
- Short, single-stranded sequences of DNA that are radioactively or fluorescently labeled and used to locate specific alleles.
Quick-Fire Flashcards (5)
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What temperature is used during the denaturation stage of PCR?
What are sticky ends?
Why is standard DNA polymerase not used in PCR?
What is a promoter region?
What is gel electrophoresis used for?
Exam-Style Questions & Mark Schemes (3)
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- Q1
Describe how a gene can be isolated using reverse transcriptase.
Click “Check Mark Scheme” to compare your answer, Cells producing the desired protein (e.g., beta cells in the pancreas for insulin) contain high concentrations of the corresponding mRNA. The mRNA is extracted. Reverse transcriptase is added, which uses the mRNA as a template to synthesize a complementary single strand of DNA (cDNA). DNA polymerase then synthesizes the second strand, forming double-stranded DNA of the required gene.
- Q2
Explain the role of marker genes in producing genetically modified bacteria.
Click “Check Mark Scheme” to compare your answer, Marker genes (e.g., antibiotic resistance or fluorescent genes) are inserted into the plasmid vector alongside the desired gene. After transformation, bacteria are grown on a medium containing the antibiotic (or exposed to UV light). Only bacteria that successfully took up the recombinant plasmid will express the marker gene and survive (or fluoresce), allowing them to be identified and cultured.
- Q3
Outline the steps involved in PCR.
Click “Check Mark Scheme” to compare your answer, 1) Denaturation: Heat DNA to 95°C to break hydrogen bonds and separate strands. 2) Annealing: Cool to 55°C to allow primers to bind (anneal) to the complementary sequences at the ends of the DNA fragments. 3) Extension: Heat to 72°C, the optimum temperature for Taq polymerase, which adds free nucleotides to synthesize new complementary strands.
Common Exam Questions (3)
What is a restriction endonuclease?
A restriction endonuclease is an enzyme that recognises a specific palindromic base sequence (recognition site) on DNA and cuts the sugar-phosphate backbone, often leaving unpaired 'sticky ends' that allow complementary DNA fragments to anneal.
What is the purpose of PCR (Polymerase Chain Reaction)?
The polymerase chain reaction (PCR) is an automated in vitro method used to amplify a target DNA fragment exponentially through repeated cycles of heating to separate strands (95°C), cooling to anneal primers (55°C), and extending new strands with Taq DNA polymerase (72°C).
What is a vector in genetic engineering?
A vector is a carrier molecule, most commonly a bacterial plasmid or a bacteriophage virus, used to transport a foreign DNA fragment into a host cell during transformation.
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