Investigating diversity

Comparison of observable characteristics:

  • Traditionally genetic diversity was measured by observing the characteristics or organisms
  • This method is based on the fact that each observable characteristic is determined by a gene or genes
  • Using observable characteristics has its limitations because a large number of them are coded for by more than one gene - they are polygenic
  • This means they are not discrete from one another but rather vary continuously
  • It is often difficult to distinguish one from another
  • Characteristics can also be modified by the environment
  • Height in humans for example is determined by a number of genes
  • However, environmental factors such as diet can influence the actual height of an individual

Comparison of DNA base sequences:

  • DNA sequencing is now routinely done by automatic machines and the data produced analysed by computers
  • In these computerised systems, each nucleotide base can be tagged with a different coloured fluorescent dye
  • This produces a series of coloured bands, each of which represents one of the four nucleotide bases
  • We can measure the genetic diversity of a species by sampling the DNA of its members and sequencing it to produce a pattern of coloured bands
  • Analysis of these patterns allows us to compare one species with another or one individual with another of the same species to determine how diverse they are
  • When one species give rise to another species during evolution the DNA of the new species will initially be very similar to that

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Investigating diversity

Comparison of observable characteristics:

  • Traditionally genetic diversity was measured by observing the characteristics or organisms
  • This method is based on the fact that each observable characteristic is determined by a gene or genes
  • Using observable characteristics has its limitations because a large number of them are coded for by more than one gene - they are polygenic
  • This means they are not discrete from one another but rather vary continuously
  • It is often difficult to distinguish one from another
  • Characteristics can also be modified by the environment
  • Height in humans for example is determined by a number of genes
  • However, environmental factors such as diet can influence the actual height of an individual

Comparison of DNA base sequences:

  • DNA sequencing is now routinely done by automatic machines and the data produced analysed by computers
  • In these computerised systems, each nucleotide base can be tagged with a different coloured fluorescent dye
  • This produces a series of coloured bands, each of which represents one of the four nucleotide bases
  • We can measure the genetic diversity of a species by sampling the DNA of its members and sequencing it to produce a pattern of coloured bands
  • Analysis of these patterns allows us to compare one species with another or one individual with another of the same species to determine how diverse they are
  • When one species give rise to another species during evolution the DNA of the new species will initially be very similar to that

Comments

No comments have yet been made