Agenda
• Today, doing labs 8 and 9a.
Informal Lab Report:
• Due in 1 Week! See the worksheet and insructions
last week.
Microworlds:
• 6 new and 4 old Microworlds are due in 2 weeks!!
Time to work on it next week, maybe some today
depending on your speed today.
• Strawberries, onion root & whitefish mitotic slides
are available for Microworlds.
Lab 9a: Cell Cycle and Mitosis
• Read background in lab
carefully
• You should get this info
in lecture
Cell Cycle:
• Interphase: G1, S, G2
• Cell may renter cell cycle or leave cell
cycle (G0)
G2
S
Mitosis
G1
Cytokinesis
•DNA replicated in S
•Nuclear division =Mitosis
•Cell division =cytokinesis
G0
MITOSIS ANIMATION
Actual MITOSIS photography
Lab 9a: Cell Cycle and Mitosis
• CELL CYCLE = entire life
of cell, including
division
– Interphase = not dividing
– Mitosis = nuclear
division
– Cytokinesis = cell
division
Interphase (before Mitosis)
• EVENTS:
– G1: Cell grows and prepares
to copy DNA
– S: Cell copies its DNA
– G2: Cell prepares to divide
• APPEARANCE:
– Chromatin (DNA) not
condensed into
chromosomes – WHY?
– Nuclear envelope present
MITOTIC PHASES
• Mitosis
–
–
–
–
Prophase
Metaphase
Anaphase
Telophase
• Cytokinesis
Prophase
EVENTS:
1. Chromatin condenses into
chromosomes
2. Chromatids visible
3. Nuclear envelope dissolves
4. Centrioles (Spindle fibers)
move to opposite poles
APPEARANCE:
• Nucleus looks blotchy
(chromosomes)
• Nuclear envelope dissolves
Metaphase
EVENTS:
1. Chromosomes line up
in center of cell
APPEARANCE:
•
•
Dark chromosomes
lined up in center of
cell
No nucleus
Anaphase
EVENTS:
1. Spindle fibers shorten
2. Chromosomes are pulled to
opposite poles of cell
APPEARANCE:
• Two sets of chromosomes
visibly separated from each
other
Telophase
EVENTS:
1. Chromosomes unwind
2. New nuclear envelope
reforms
APPEARANCE:
• Two dark areas of chromatin
present at opposite ends
Cytokinesis
EVENTS:
• Animals: Daughter cells
pinch apart at cleavage
furrow
• Plants: Cell plate forms
in center of cell
APPEARANCE:
• Two new (usually
smaller) cells form
Cell Division in Plants
Plants differ from animals
• Plant cells have no
centrioles
• Plant cells differ in
Cytokinesis:
– a cell wall forms between
the dividing cells
– called a cell plate
Mitosis Review
Lab 9a: Mitosis
Ex. 1: Modeling Mitosis with either Clay (1a) or Pop
Beads (1b). Only do 1a or 1b.
Ex.2: Observing mitosis in plant cell slides
•
Practice this f/ lab quiz & final!
Ex.3: Observing mitosis in
whitefish cells
•
May instead answer which is
easier plant or animal? Why?
Ex.4: Estimating time spent
in each phase
Lab 8, Ex. 4: Estimating the time
spent in each phase of Mitosis
• Identify the phase for 25 cells
–
–
–
–
Get 3 other people’s data (100
cells total)
Calculate the percent time
spent in each phase
(If you have 5 cells/100 in
metaphase, then the cells
spend ~5% of the time in
metaphase.)
Check your answer. If its off,
you need to spend more time
identify the phases!
Lab 8, Exercise 1: DNA Extraction
• You can extract DNA from
practically everything
• Strawberries, peas, your lab
partner’s brain!
The Lysis Buffer
• Contains water and a buffer
• A Detergent
– to dissolve the membranes so we can extract DNA
– The cell wall is not a problem as DNA in water can move
through it
• A Salt
– Causes proteins and carbohydrates to precipitate out of
solution
– We only want DNA
DNA Extraction
• Since your lab partner
may object to your
isolating brain DNA,
we’ll use strawberries
• Squash strawberry to
increase the surface
area exposed to
detergent
• It simply makes smaller
pieces
DNA Extraction
• Add lysis buffer and
continue squashing
• Filter mixture through
filter paper (coffee
filter)
• The DNA will be in the
filtrate solution you
capture
DNA Extraction
• Pour ice-cold alcohol
(equal volume to
strawberry filtrate)
down side of tube to
precipitate DNA
• Keep it cold!
DNA Extraction
• It will appear like slimy snot between the alcoholwater interphase
• Skip steps 13-14, viewing
your DNA under the
microscope.
If desired, here are two Home DNA
Extraction sites:
• http://www.pbs.org/wgbh/nova/teachers/acti
vities/2809_genome.html
• http://biology.about.com/c/ht/00/07/How_Ex
tract_DNA_Human0962932481.htm
Lab8, Exercise 2: Transcription,
Translation, Mutation Practice
• Follow directions
• Remember base-pairing
rules:
– DNA  DNA
– DNA  RNA
• Know how to use this
table but do not
memorize it!
Second base
C
U
UUU
U
UUC
UUA
UUG
Phe
Leu
CUU
C
A
CUC
CUA
Leu
UAU
UCU
UCC
UCA
Ser
UAC
CAU
CGU
CCC
CCA
Pro
CAC
CAA
AAU
AUC lle
ACC
AUA
ACA
GUA
GUG
U
C
CCU
ACU
Val
UGC
Cys
UAG Stop
AUU
GUC
UGU
UCG
CAG
GUU
Tyr
UGA Stop A
UGG Trp G
CCG
Met or
start
G
UAA Stop
CUG
AUG
G
A
Thr
AAC
AAA
ACG
AAG
GCU
GAU
GCC
GCA
GCG
Ala
GAC
GAA
GAG
His
Gln
Asn
Lys
Asp
Glu
CGU
CGA
U
Arg
G
CGG
AGU
AGC
AGA
AGG
C
A
Ser
Arg
U
C
A
G
U
GGC
C
Gly
GGA
A
GGG
G
GGU