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19.1.219 · Genetic Technology

Genetic Engineering — Cambridge AS & A Level Biology 9700 Revision Notes & Topical Questions

5 min read 10 parts Lesson 3 of 20 1 quiz

📚 Cambridge AS & A Level Biology 9700 Hub / Topical Revision
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19.1.2 Genetic Engineering — CAMBRIDGE AS & A LEVEL BIOLOGY 9700 — REVISION NOTES notes: Outline the steps of genetic engineering and the materials needed.Genetic engineering — a technique used deliberately to modify a specific characteristic of an organism.A gene with the desire…

  • Advantages
  • Synthetic biology
  • Marker gene
  • Transgenic organism
  • Complementary
  • Electrophoresis

Part 1 of 8What genetic engineering is

Genetic engineering
  • Genetic engineering a technique used deliberately to modify a specific characteristic of an organism.
A gene with the desired characteristic is removed from one organism and transferred, using a vector, to another organism where it is expressed.
The engineered organism contains recombinant DNA and is a genetically modified organism (GMO).

Part 2 of 8Steps in genetic engineering

1
Identify the desired gene.
2
Isolate the gene.
  • Cut it from a chromosome with restriction endonucleases.
  • Make cDNA from mRNA with reverse transcriptase.
  • Synthesise the gene artificially from nucleotides.
3
Multiply the gene using the polymerase chain reaction (PCR).
4
Transfer it into the organism using a vector (plasmid, virus or liposome).
5
Identify cells with the new gene using a marker, then clone them.

Part 3 of 8What genetic engineers need

Enzymes
  • Enzymes restriction endonucleases, DNA ligase, reverse transcriptase.
    • (and DNA polymerase)
Vectors
  • Vectors deliver genes into a cell, e.g. plasmids, viruses and liposomes.
Markers
  • Markers genes coding for identifiable substances that can be tracked.
  • GFP — green fluorescent protein, which fluoresces under UV light.
  • GUS — glucuronidase, which turns colourless substrates into coloured or fluorescent products.
A promoter is also added so the gene is expressed in the host.

Part 4 of 8Example: human insulin in bacteria

Before 1982, diabetics used insulin from pigs and cattle, which differs slightly from human insulin and can cause immune reactions.
The human insulin gene (or a synthetic copy) is placed in a plasmid with a promoter and inserted into E. coli or yeast.
The cells are grown in large fermenters and the insulin is purified.
Advantages
  • Advantages a human protein, no risk from animal pathogens, unlimited supply and acceptable to people for religious or ethical reasons.

Part 5 of 8Other applications

1
Bt maize and cotton carry a gene for a toxin from Bacillus thuringiensis, which poisons insect larvae.
2
Golden Rice makes beta-carotene, a precursor of vitamin A.
3
Gene therapy introduces a functional allele into a patient's cells; somatic therapy is not inherited, germline changes would be.
4
Transgenic animals can make human proteins in their milk.

Part 6 of 8Synthetic biology

Genetic engineering is used in synthetic biology.
Synthetic biology
  • Synthetic biology research into the design and construction of biological pathways, organisms and devices,
    • and the redesign of natural biological systems.

Part 7 of 8Evaluating GM technology

BenefitsConcerns
Higher crop yields and nutritional valueGene flow to wild plants; loss of biodiversity
Less pesticide useResistance evolving in pests or weeds
Medicines and vaccines in large amountsAllergies or unknown health effects
Crops tolerant of drought and saltHigh cost, patents and corporate control of seed

Part 8 of 8More from the specification

1
Restriction Endonucleases
  • Bacterial enzymes that recognise specific palindromic DNA base sequences and cleave double-stranded DNA molecules to produce sticky ends or blunt ends.
2
Separation of DNA Fragments via Gel Electrophoresis
  • Scientists use agarose gel electrophoresis to separate negatively charged DNA fragments according to size as they migrate toward the anode through an electric field.
3
DNA Hybridisation in Microarrays
  • Microarrays contain thousands of known single-stranded DNA probes fixed to a solid chip;
    • complementary fluorescently labelled cDNA fragments hybridise with matching sequences,
  • allowing high-throughput gene expression analysis.
4
Restriction Endonucleases
  • Bacterial enzymes that recognise specific palindromic DNA base sequences and cleave double-stranded DNA molecules to produce sticky ends or blunt ends.
5
Separation of DNA Fragments via Gel Electrophoresis
  • Scientists use agarose gel electrophoresis to separate negatively charged DNA fragments according to size as they migrate toward the anode through an electric field.
6
DNA Hybridisation in Microarrays
  • Microarrays contain thousands of known single-stranded DNA probes fixed to a solid chip;
    • complementary fluorescently labelled cDNA fragments hybridise with matching sequences,
  • allowing high-throughput gene expression analysis.
7
Bacteria
  • Single-celled microorganisms, much smaller than plant or animal cells.
8
Sequence
  • The order of bases in DNA or amino acids in a protein.
9
Complementary
  • Having a matching shape.
10
Electrophoresis
  • Separation of molecules by size in an electric field
11
Microarray
  • Chip with probes used to detect many genes at once.
12
Genome
  • All the genetic information in an organism.

Key terms

TermMeaning
Genetic engineeringTransfer of a gene from one organism to another to modify a characteristic.
VectorCarrier that delivers a gene into a cell.
Marker geneGene coding for a detectable substance, used to identify modified cells.
GFPGreen fluorescent protein, fluoresces under UV light.
Synthetic biologyDesign and construction of new biological systems.
Transgenic organismOrganism containing genes from another species.

Avoid these mistakes

1
Leaving out the names of the enzymes — name restriction endonucleases, reverse transcriptase, DNA polymerase and ligase.
2
Forgetting vectors and markers — vectors transfer the gene and markers identify transformed cells.
3
Saying the engineered organism contains no recombinant DNA.
4
Confusing selective breeding with genetic engineering — selective breeding only combines existing alleles over many generations.

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