Sordaria is an ascomycetes fungus, which is an important haploid organism used in genetic research and teaching. It exists, most of its life, in a haploid state but produces structures called perithicia representing the diploid stage.
Perithicia are dark pear-shaped structures,which contain a number of sac-like structures called asci:
Images taken from: http://www.science.lander.edu/flux/Sordaria%20Tetrad%20Examples.htm
Each ascus undergoes, first, a meiotic division to produce four ascospores and then a round of mitotic division to form eight ascospores. The arrangement of the ascospores within an ascus is linear and thus reflects the precise behavior of chromosomes during the process of meiosis.
Analysis of ascospores in terms of their colour, and relative position within an ascus can be used for illustrating the phenomenon of crossing over centromere linkage and the Mendelian principles of segregation and assortment.
After completing this lab, you should know:
1. The procedure for setting up the crosses between genetically different strains of Sordaria
2. How to calculate the map distance between a gene and the centromere
2. microscope slides
3. cover slips
4. sterile toothpicks
5. Sordaria strains
6. media for crossing strains
7. marking pen
Preparation (to be carried out during lab 4) Two weeks prior to this lab period you completed Section I.
Procedure (Section I)
i) Prepare media plates and ii) Set up the crosses with the wild-type and tan strains.
1. With a marking pen, divide the bottom of a sterile medium plate into two equal portions. Label alternatively wild and tan.
2. Using a sterile toothpick, remove a small piece of mycelium from the stock plate labeled "wild".
3. Place it on the surface of the medium plate labeled "wild". Place it away from...