The Thread of Life F334

General Thread of Life revision.

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DNA Fingerprinting

DNA fingerprinting can be used to determine who a certain sample of genetic material came from. Every DNA profile is different as everybody has a unique genetic code, however this isn't the case for identical twins who share the same DNA and would produce an identical profile. 

The DNA sample is taken and cut into fragments using restriction enzymes (endonucleases) and then separated using a process known as gel electrophoresis. Each fragment is then marked with a probe and exposed using x-ray film or ultraviolet light. 

There are however some ethical issues surrounding the use and storage of genetic data:


  • Who has access to personal genetic information?
  • Who owns and controls the information? 
  • Who owns the genetic material?

DNA Testing 

  • Should parents have the right to have their children tested? 
  • Should tests be performed for genetic diseases?
  • Should an individual always be given access to their genetic information? 
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The Effect of Concentration on Reaction Rate

Using a concentration-time graph the order of a reaction can be determined. 

  • If the reaction is zero order the concentration will decrease uniformly as time increases
  • If the reaction is first order the graph will be curved however will have constant half lives
  • If the reaction is second order the graph will be curved but won't have a constant half life 

The order of reaction can also be determined by a rate-concentration graph.

  • If the reaction is zero order the rate will remain constant as concentration increases
  • If the reaction is first order the rate will increase uniformly as concentration increases
  • If the reaction is second order the graph will be curved 


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Enzyme-catalysed reactions usually have different rate equations at high and low substrate concentrations. At low substrate concentration there are plenty of active sites available for the substrate to bind to, so doubling the substrate concentration will double the rate of reaction. The reaction will therefore be first order with respect to the substrate concetration. 

At high concentrations of substrate all of the active sites on the enzymes will be saturated. The reaction therefore becomes zero order with respect to the substrate concentration because doubling the concentration of substrate will have no effect at all on the rate of reaction.

Enzymes are used in industry because: 

  • They're specific and can select a specific substrate from a feedstock 
  • They work effectively at low temperatures which can reduce energy costs 
  • They work well in aqueous environments which reduces the need to use organic solvents which can damage the environment
  • They can convert the rectants to products in a one-step reaction which increases the atom economy of the reaction
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