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Unit 2: How does inheritance impact on diversity?
Quick questions on DNA manipulation: PCR and gel electrophoresis: VCE Biology Unit 2
9short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is gel electrophoresis?Show answer
Gel electrophoresis separates DNA fragments by size. Used to check PCR products, compare DNA profiles, or sort DNA pieces before sequencing.
What is dNA profiling?Show answer
DNA profiling (also called DNA fingerprinting) uses regions of the genome where individuals differ predictably.
What is outcome?Show answer
Each cycle doubles the amount of target DNA: 1 to 2 to 4 to 8 to ...
What is visualisation?Show answer
The amplified product is then loaded into a gel (next section) or sequenced.
What are strengths?Show answer
Extreme sensitivity (single molecules can be amplified), speed (a few hours from sample to product), and specificity (primers ensure only the target region is amplified).
What are limitations?Show answer
Sensitivity is also a weakness: contamination with stray DNA can be amplified just as easily as the target. PCR requires knowledge of the target sequence to design primers.
What is q1?Show answer
Outline the three temperature steps of a PCR cycle and state what happens at each. [3 marks]
What is q2?Show answer
A PCR reaction begins with 5 copies of a target DNA. Calculate the number of copies after 30 cycles, assuming 100 percent efficiency. [2 marks]
What is q3?Show answer
A gel electrophoresis run shows four DNA bands at 200, 500, 1200 and 3000 bp. (a) State which band travelled furthest from the well and justify. (b) Describe how a DNA ladder is used to estimate fragment size.