Introduction to Studying DNA

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Chapter 4

• Introduction to Studying DNA

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Sources of DNA-Prokaryotic DNA

• Nearly all prokaryotes have a single circular
  chromosome
• Contained within a conglomeration of ribosomes
• Other proteins related to transcription and
  translation
• Region called the nucleoid
• Opposed to the well defined, double membrane
  bound eukaryotic nucleus
• Certain exceptions
• Borrelia burgdorferi and the genus Streptomyces
  contain linear chromosomes, like the eukaryotes
• Vibrio cholerae, the causative agent of cholera
• Has two circular chromosomes
• Smaller of which contains most of the genes
  responsible for virulence

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Sources of DNA-Prokaryotic DNA

• Plasmids
• Small (about 1 to 10 thousand base pairs),
  circular pieces of DNA
• Replicated by the host's DNA replication
  machinery
• Genes are not absolutely critical for general
  survival
• In nature
• Usually contain special genes that confer some
  type of selective advantage such as antibiotic
  resistance
• Called the R plasmids
• Virulence
• In genetic engineering artificially introduced
  plasmids carry genes to be expressed and studied
• They are Transformed-take up foreign DNA and
  express the genes on the newly acquired DNA

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Sources of DNA-Bacterial Cell Culture

• Bacterial cells must be provided with an
  environment to grow
• Broth
• Liquid medium
• Agar
• Solid medium

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Sources of DNA-Bacterial Cell Culture

• Agar
• Unbranched polysaccharide
• Obtained from the cell walls of some species of
  red algae or seaweed
• polymer made up of subunits of the sugar
  galactose
• Agar polysaccharides serve as the primary
  structural support for the algae's cell walls

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Sources of DNA-Mammalian Cell Culture