A Level Biology - Polymerase Chain Reaction

What is required in a PCR reaction mixture?

• DNA ligase, helicase, and Okazaki fragments

• Restriction enzymes, primers, and mRNA

• DNA polymerase, primers, nucleotides, and a DNA template

• RNA polymerase, ribosomes, and tRNA

What is the purpose of PCR?

• To cut DNA into smaller fragments

• To amplify specific DNA sequences

• To sequence an entire genome

• To separate DNA fragments by size

Which enzyme is essential for PCR?

• Taq polymerase

• DNA ligase

• Restriction enzymes

• RNA polymerase

What happens during the annealing step of PCR?

• DNA strands separate

• Primers bind to complementary DNA sequences

• DNA polymerase extends the new DNA strand

• The temperature reaches 95°C

Why is Taq polymerase used in PCR?

• It can copy RNA instead of DNA

• It does not require primers

• It is heat-stable and works at high temperatures

• It can repair DNA damage

What would happen if no primers were added to the PCR reaction?

• DNA would still amplify, but at a slower rate

• DNA would be denatured but not copied

• The reaction would produce double-stranded RNA

• The reaction would amplify the entire genome

Why does DNA amplification in PCR eventually plateau?

• All template DNA has been copied

• The reaction reaches equilibrium

• Reagents become limiting, and polymerase loses efficiency

• The temperature becomes too high

How can PCR be modified to amplify RNA instead of DNA?

• Use an RNA polymerase instead of DNA polymerase

• Add restriction enzymes before amplification

• First convert RNA to DNA using reverse transcriptase

• Use a lower annealing temperature

What feature of primers ensures specificity in PCR?

• Their length and complementary sequence to the target DNA

• Their ability to bind anywhere on the genome

• Their ability to extend DNA strands

• Their resistance to high temperatures

Which of the following is NOT an application of PCR?

• Diagnosing genetic diseases

• Creating genetically modified organisms

• Amplifying ancient DNA from fossils

• Synthesizing new DNA sequences without a template