Sordaria Crossing Over

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Sordaria Crossing Over

• This activity involves observing the results
  of crossing over in a fungus, Sordaria. A cross
  between two haploid strains of Sordaria produces
  spores of different colors.

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• Where the growing filaments of the two strains
  meet, fertilization occurs and zygotes form.
  Meiosis occurs within fruiting bodies to form
  haploid ascospores, spores contained in asci
  (special sacs). Then one mitotic division doubles
  the number of ascospores to eight.

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• Four black ascospores in a row next to four tan
  ascospores in a row indicates that crossing over
  has NOT occurred.  Any other arrangement of
  ascospores indicates that crossing over has taken
  place.

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• Study the following picture of Sordaria to
  determine if crossing over has occurred in the
  asci.  If the ascospores are arranged 4 dark/4
  light, count the ascus as "No crossing over." If
  the arrangement of ascospores is in any other
  combination, count it as "Crossing over."

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• Examples of Sordaria Octads
• By Fordyce G. Lux IIIProfessor of BiologyLander
  UniversityWe thank you for your excellent work.

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