Biotechnology and Experimental Skills
This domain tests recombinant DNA technology, PCR, electrophoresis, tissue culture and the design and interpretation of experiments. Expect questions on controls, variables, graphical analysis and Rf calculations.
Biotechnology
Recombinant DNA uses restriction enzymes to cut DNA and DNA ligase to join fragments. A vector, often a plasmid, carries the gene into a host cell. PCR amplifies DNA through denaturation, primer annealing and extension, doubling the target each cycle. Gel electrophoresis separates DNA by size; DNA is negatively charged and moves towards the anode. Tissue culture grows cells or explants on sterile nutrient media. Transgenic organisms raise ethical and ecological issues.
Experimental skills
An experiment has an independent variable, a dependent variable and controlled variables. A control group is treated identically except for the independent variable. Validity depends on controlling relevant variables; reliability improves with repeats; accuracy concerns closeness to the true value. Rf = distance moved by the solute ÷ distance moved by the solvent front.
Worked example
A pigment travels 48 mm while the solvent front travels 80 mm. Rf = 48 ÷ 80 = 0.60. Rf is dimensionless and must be less than 1. Comparing it with standard Rf values helps identify the pigment, provided the solvent and conditions are the same.
Traps
A control group is not the same as a controlled variable. Keep temperature, pH and solvent constant in chromatography. Do not read a graph beyond its axes, and always include units. Confusing precision with accuracy costs marks.
Data interpretation
Describe trends, quote data, and explain using biological principles. State whether a conclusion is supported by the evidence and identify sources of error.