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
Sample of all black spores
• 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 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
the number
ascihave
that have
notover
crossed
CountCount
the number
of asciofthat
crossed
Youlooking
are looking
for 4:4orcombination
You are
for 2:2:2:2
2:4:2 combination.
7 asci display
crossing over
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