Sordaria Meiosis Lab

Sample of Sordaria in petri dish

Introduction For the following slides, please refer to the background information on Sordaria and their life cycle in your meiosis packets, pages 7 and 8

To the right is a photo of asci that resulted from a cross between two black strains that is both parental strains had black colored spores All of the 8 asci spores are black Sample of all black spores

Sample of tan spores To the right is a photo of asci that resulted from a cross between two tan parental strains. All of the 8 asci spores are tan.

Black and tan cross To the right is a photo of asci that resulted from a cross between black and tan strains. Some asci have 4 black spores and then 4 tan (4:4) Some asci display a 2:4:2 or 2:2:2:2 sequence

No Recombination Asci 4:4

Recombinant Asci (Crossing over has occurred) 2:2:2:2 or 2:4:2

Sample Problem

Count the number of asci that have crossed over You are looking for 2:2:2:2 or 2:4:2 combination. 7 asci display crossing over Count the number of asci that have not crossed You are looking for 4:4 combination 4 asci display crossing over 11 total asci

Calculating distance between the tan and black genes Number of asci crossed over: 7 Number of asci not crossed over: 4 Total asci: 11 Calculations (number of crossover) = 7/11 =.64 (total asci) 64% crossover

Part II: Crossing Over in Sordaria Now it’s your turn

Directions for lab Observe the following 9 photos of sordaria asci. On page 9 of your packet keep track of the number of crossover, and no crossover asci that you see. The writing space is a little tight Do not count the asci that are entirely one color (ie, all tan spores or all black spores), there represent a double crossover! You should count close to 100 asci when you are done with all of the photos! Please try to guess (when possible) on the asci that may be cut off in the diagrams. This is due on Wednesday 11/8/06

The End