AP LAB #3
part C
Crossing Over during Meiosis
in Sordaria… counting map
units
Sordaria fimicola is a type of
FUNGUS, found in the group known
as ASCOMYCOTA
“Sac
fungi”
The shared derived character that
defines the Ascomycota is the
ascus. It is within the ascus that
nuclear fusion and meiosis take
place.
Ascus are
found in
here… in
the
ascocarp!
Sordaria fimicola~ ASCOMYCOTA
See, here
they are…
ASCI!
Sordaria fimicola~ ASCOMYCOTA
This is what
it looks
under a
scanning emicroscope!
Sordaria fimicola~ ASCOMYCOTA
Here they are… ASCI! ~ they hold
ASCOSPORE
Sordaria fimicola~ ASCOMYCOTA
Here they are… ASCI! ~ there are
chromosomes inside those dots!!
In the ascus, meiosis occurs, followed by
a round of mitosis. This leaves eight
nuclei, and eventually eight ascospores
THERE ARE CHROMOSOMES
INSIDE THOSE SPORES… AND
WITHIN THE CHROMATIN,
THERE ARE GENES….
These genes code for traits…
COLOR
Ascospores are formed within the ascus
by an enveloping membrane system,
which packages each nucleus with its
adjacent cytoplasm and provides the site
for ascospore wall formation
Sordaria fimicola~ ASCOMYCOTA
Sordaria fimicola~ ASCOMYCOTA
S phase
Meiosis I
Meiosis II
Sordaria fimicola~ ASCOMYCOTA
Sordaria fimicola~ ASCOMYCOTA
Sordaria fimicola~ ASCOMYCOTA
Sordaria fimicola~ ASCOMYCOTA
Sordaria fimicola~ ASCOMYCOTA
No X-over
How many DID NOT
crossover?
Sordaria fimicola~ ASCOMYCOTA
Did X-over
How many DID crossover?
Sordaria fimicola~ ASCOMYCOTA
How many DID crossover?
Total counted
X 100
Sordaria fimicola~ ASCOMYCOTA
349
609
X 100
Sordaria fimicola~ ASCOMYCOTA
. 573 X 100 = 57.3
Sordaria fimicola~ ASCOMYCOTA
Divide this number
by 2
How many DID crossover?
Total counted
X 100
Sordaria fimicola~ ASCOMYCOTA
. 573 X 100 = 57. 3 / 2
Sordaria fimicola~ ASCOMYCOTA
= 28 .65
Sordaria fimicola~ ASCOMYCOTA
= 28 .65 this means
28.65 MAP UNITS
Sordaria is a haploid organism
for the majority of its life cycle
It becomes diploid only
when mycelia fuse and
two different types of
haploid nuclei form a
diploid nucleus.