Electrophoresis investigation: revision

Cards (25)

  • Dependent Variable: The variable that is measured, in order to determine whether it changes in response to changes in the independent variable.
  • In an experiment to determine whether adding a fertiliser to plants increases their growth rate, what is the dependent variable?
    growth rate
  • Accuracy: The closeness of a measurement to the true value.
  • Independent Variable: The variable that is deliberately changed in order to determine whether it causes a change in the dependent variable.
  • In an experiment conducted to determine whether adding a fertiliser to plants increases their growth rate, what is the the independent variable?
    whether fertiliser was added to a plant or not
  • Precision: A measure of how close together a series of measurements are.
  • Random error affects the precision of a measurement, or the reliability of experimental results
  • Systematic errors affect the accuracy of a measurement, or the validity of experimental results
  • Reliability: The degree of which the results of an experiment are consistent or reproducible.
  • PCR process is repeated many times, each time number of strands of DNA is doubled. PCR occurs in a machine called a thermal cycler (thermocycler).
  • Agarose Gel Electrophoresis uses an agarose gel to separate molecules by moving them in an electric field, molecules are separated according to size.
  • DNA that is placed in a gel electrophoresis is usually cut with a restriction enzyme to produce DNA fragments of various sizes, or only specific regions are amplified.
  • DNA is negative due to phosphate groups in sides of the DNA ladder.
  • The larger the fragment, the slower it moves through the gel.
  • Electric current causes negatively charged DNA fragments to move towards positive end of gel.
  • different densities of gel are used to separate different samples of DNA (thick gels for samples containing many small fragments of DNA, thin gels for samples containing large fragments of DNA).
  • The gel or the DNA samples contain a fluorescent dye making the DNA visible under UV light. (ethidium bromide)
  • the gels are submerged in a buffer solution that allows the flow of the electric current using ions and stabilises pH
  • How DNA is obtained for electrophoresis: 1. collect cells 2. prepare them for electrophoresis either with restriction enzymes or PCR to amplify a specific fragment
  • Molecular ladders are samples of DNA of known lengths.
  • Gel electrophoresis is used for: restriction fragment analysis, paternity testing, and DNA fingerprinting
  • Restriction fragment analysis (aka restriction mapping) is used to what?
    map an unknown segment of DNA by breaking it into pieces and identifying locations of the break points
  • Restriction fragment analysis relies on restriction enzymes
  • validity: whether you measured what you intended to measure
  • reliability: how consistent your results were