9700 · 19.1
Principles of genetic technology flashcards
Revision flashcards for Cambridge 9700 Principles of genetic technology (syllabus 19.1). Flip, recall, then mark a real past-paper question.
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What is the primary goal of recombinant DNA technology?
To join DNA molecules from two different species and insert them into a host organism to create new genetic combinations, often to produce a specific protein or confer a new trait.
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What is the function of a restriction endonuclease?
It acts as 'molecular scissors', recognizing and cutting DNA at specific palindromic sequences called restriction sites. This can produce 'sticky ends' or 'blunt ends'.
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What is the role of DNA ligase in genetic engineering?
It acts as 'molecular glue', catalysing the formation of phosphodiester bonds to permanently join DNA fragments, such as inserting a gene into a plasmid vector.
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Why are 'sticky ends' useful in creating recombinant DNA?
They are short, single-stranded overhangs that are complementary to other sticky ends created by the same restriction enzyme. This allows a gene and a vector to anneal (join via hydrogen bonds) easily before being permanently sealed by DNA ligase.
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What is a vector in genetic engineering? Give two examples.
A vector is a DNA molecule used as a vehicle to carry foreign genetic material into a host cell. Common examples include plasmids and viruses (e.g., bacteriophages, retroviruses).
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What are the three main steps of a PCR cycle, including temperatures?
1. **Denaturation** (~95°C): Separates double-stranded DNA. 2. **Annealing** (~50-65°C): Allows primers to bind to the template DNA. 3. **Extension** (~72°C): Taq polymerase synthesises new DNA strands.
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Why is Taq polymerase essential for PCR?
Taq polymerase is a thermostable (heat-stable) enzyme, originally isolated from the bacterium *Thermus aquaticus*. It can withstand the high temperatures of the denaturation step (~95°C) without being denatured, allowing the PCR process to be automated through many cycles.
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What is the principle behind gel electrophoresis for separating DNA fragments?
DNA fragments are negatively charged (due to phosphate groups) and are loaded into a gel matrix. When an electric field is applied, the fragments migrate towards the positive electrode (anode). Shorter fragments move faster and further through the gel pores than longer fragments, separating them by size.