Biology / A2 level
PCR amplifies a selected DNA region through repeated cycles using primers, nucleotides and a suitable polymerase.
PCR amplifies a selected DNA region through repeated cycles using primers, nucleotides and a suitable polymerase. Electrophoresis separates DNA fragments mainly by size under defined gel conditions, while sequencing reveals base order rather than merely fragment length.
Recombinant DNA methods and gene editing can alter genetic information for research and applications. Successful DNA modification does not automatically ensure the intended expression, phenotype or ecological outcome. Controls, off-target assessment and context-specific evaluation are necessary when interpreting results.
An ideal PCR model starts with one target copy and doubles it in each of five cycles. How many copies result?
Ideal doubling gives 1×2⁵=32 target copies; real efficiency can be lower.
Using the worked example as supplied data, predict the effect of changing one condition. Draw a labelled model, record your reasoning and identify a variable that would need controlling. No human, animal or microbial experiment is required.
Related simplified PhET model. Explain what it represents and what the living system does differently.
The region targeted for amplification
Primers bind suitable sequences flanking the target and provide starting points for synthesis.
32
Ideal doubling gives 1×2⁵=32 target copies; real efficiency can be lower.
No
Different sequences can share a length; further controls or sequence analysis may be needed.