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A L L S L I D E S , I N F O F R O M V I D E O S A N D
Q U E S T I O N T O P I C S W I L L B E O N E X A M # 3
C O M P L E T E Q U E S T I O N S F O R E A C H S E C T I O N . 
S E N D T H E C O M P L E T E D Q U E S T I O N S B Y 4 P M
T U E S D A Y , J U N E 2 1 , T O : blinderl@mccc.edu
W O R K S U B M I T T E D M U S T B E I N T H E
S T U D E N T S O W N W O R D S

 READ CHAPTER 12 IN TEXTBOOK



cell division = reproduction of cells
All cells come from pre-existing cells
Thought question (do not turn in)
What pre-existing cells did your cells come from?

 Unicellular organisms  division of 1 cell reproduces organism
 Binary fission
a. How frequently do some bacteria divide?
b. How does this explain their ability to expand their numbers quickly?


Why cells reproduce

Development/Growth
Example: embryo  adult

Replacement
Example: stomach lining is continually replaced

Repair
Example: repair of burn



Watch the video http://www.youtube.com/watch?v=f7cXeWxxfD4
 Sea stars can reproduce cells in a way that humans cannot – view and understand.

FYI


Three Hundred Million Cells Die In Your
Body Every Minute
It does sounds like a lot but this is actually less than
0.0001% of the amount of cells being replaced in your body every day. (about 10-50 trillion cells are replaced in your body every day)

 chromosome = strand of DNA

2 sets of 23 chromosomes in humans = 46
 genome = All DNA in a single cell

 single chromosome (prokaryotes) many chromosomes (eukaryotes)
20 µm
View the data on the website http://morgan.rutgers.edu/morganwebframes/level1/page2/Chr omNum.html
Explore the number of chromosomes in each type of organism’s cells. a.
Is there a correlation between chromosome number and intelligence? Provide evidence to support your claim.

This is an electron micrograph of the
46 chromosomes in a human cell.

 chromatin complex of DNA and protein
20 µm
Chromatin normally looks diffuse - hard to see individual chromosomes



Haploid – a cell with one set of chromosomes
Diploid – a cell with two sets of chromosomes

http://www.ncbi.nlm.nih.gov/books/NBK9863/ b.
c.
a.

Look carefully at the list – are these diploid, or haploid chromosome numbers?
How many chromosomes are in the sperm of a fruit fly?
Which organisms have genome sizes similar to humans (Mb size is multiplied by 1 million for total size)



Mitosis – cell division process to replicate cells

Ex. Skin cells do this
Meiosis – cell division process to generate unique haploid cells

Ex. Spermatogenesis, oogenesis



BE ABLE TO DISTINGUISH BETWEEN
MITOSIS AND MEIOSIS
Somatic cells= body cells (2 trillion in adult)

 two sets of chromosomes (pairs= diploid )
Produced by mitosis - 1 diploid cell  2 identical diploid cells

Skin cells produced by mitosis 
 Gametes sperm and eggs

 have one set = haploid
Produced by meiosis – 1 diploid cell  4 unique cells

Occurs only in ovaries, testes
Egg cell (oocyte) is a gamete produced by  meiosis

Identical cells
Diploid
Unique cells
Haploid

Read the textbook and study the previous slides to answer the following
QUESTION 4 a.
A fruit fly sperm contains 4 chromosomes. How many chromosomes .
Which of the cells below are diploid? (there are 6)
- fruit fly wing cell
- haploid cell
- gamete from a fern plant
- fertilized whale egg
- cell produced by meiosis
- sperm of frog
- monkey liver cell
- plant pollen (contains sperm)
- fish somatic cell
- human embryo cell
- cell with 2 sets of chromosomes
- unfertilized bird egg b. Which of the following terms are associated with mitosis
(there are 6)
- sperm - somatic - genetically identical
- diploid
- unique cells
- ovary
- liver cell
- 1 set of chromosomes - 4 daughter cells
- 2n
- 46 chromosomes
- gametes


Nuclear division = division of the nucleus

Cytokinesis = division of cytoplasm
View the video to compare http://www.youtube.com/watch?v=rgLJrvoX_qo
&NR=1

When both have occurred, there are 2 new cells, each identical to the “parent” cell

Interphase ~
90% of a cell’s time cell is doing its normal activity during this time
S
(DNA synthesis)
G
1
Mitosis -
~ 4o min cell is involved in replicating to make 2 new cells
G
2
A cartoon showing the time cell spends in interphase and mitosis. Note that mitosis is short

 Now, we will examine the individual steps in the cell cycle. Give yourself enough time to understand each step before proceeding.

INTERPHASE (~90% of the cell’s time in the cell cycle, not part of mitosis)



G1 phase – cell grows, gets ready
S phase – DNA replicates
G2 phase – cell grows, gets ready
G
1
S
(DNA synthesis)
G
2
Watch the cell cycle video http://www.youtube.co
m/watch?v=O3_PNiL
WBjY


Signs of interphase?


Note the distinct nuclear membrane
Note that the chromosomes inside the nucleus are not visible (they are too thread-like at this stage to see)
Cell membrane
Photo of a fish cell

 Chromosomes replicate to form:
 Sister chromatids = 2 for each chromosome, they are attached at the centromere (constricted region)
This is one chromosome that has replicated into a pair of sister chromatids

All 46 chromosomes in a human cell have been replicated to form sister chromatids held together at the centromeres

: review the textbook and notes
a) b)
Number of chromosomes in a human sperm or egg cell
Number of chromosomes in a human fertilized egg c) Total number of sister chromatids in a human cell after
S phase of Interphase (not sister chromatid pairs, individual sister chromatids)


Prophase

Metaphase

Anaphase

Telophase
 Cytokinesis (division of cytoplasm) by late telophase

A. Chromosomes condense = they become thicker and shorter
B. Nuclear membrane breaks apart
C. Mitotic spindle forms from centrioles

A chromosome in prophase= 2 identical sister chromatids held together at centromere

Note the absence of a nuclear membrane in the cell that has entered prophase
The nuclear membrane is breaking up
A fish cell

This is a slide of onion cells with chromosomes stained red
View: condensed chromosomes in prophase and absence of nuclear membrane
Cannot see the mitotic spindle in this photo





Remember the centrioles
They have replicated and moved to opposite sides
(poles) of the cell
AND, microtubules have grown from them – the red lines – they attach to the centromeres of the sister chromatid pairs
The microtubles are called spindle fibers

 http://www.nature.com/scitable/definition/spindlefibers-304
 Scitable is a website that contains information on many aspects of biology and genetics. The components of the mitotic spindle are covered here.
 You may need to register, its free. If you do not have a textbook, the definitions on Scitable will be useful to you.

Assignment: Read the text and study the slides.
a.
b.
c.
d.
e.
Are the two sister chromatids that compose a chromosome in prophase identical?
To what structure do the mitotic spindle microtubules attach on the chromosomes?
What are the components of the mitotic spindle?
What are centrioles composed of?
What is meant by “chromosomes condense” ?
WATCH THE PROPHASE VIDEO http://www.youtube.com/watch?v=BFDSlHv3SZU


 chromosomes (still in sister chromatid pairs) line up at the metaphase plate midway between spindle’s two poles
Centrioles with spindle fibers
Chromosomes are lined up
Fish cell

Metaphase plate
Centriole with spindle fibers
The chromosomes here do not look as neat – but their centromeres are in a line on the metaphase plate

Watch the metaphase video http://www.youtube.com/watch?v=8C7Y1F1uyQs&fea ture=related a.
b.
c.
d.
How can you determine visually that a cell is in metaphase?
About how long in minutes or hours is metaphase?
Is the spindle apparatus (mitotic spindle) obvious during metaphase?
Are the sister chromatids still attached at the centromere during metaphase?



 sister chromatids separate ! They split into individual chromosomes.
Mitotic spindle shortens –to move newly separated chromosomes toward opposite ends of cell
This is tightly controlled – need a full set of chromosomes moving to each side!
Plant cell chromosomes in red

Fish cell – note that a set of chromosomes, is moving to each end of the cell. The cell also is huge


Watch the anaphase video http://www.youtube.com/watch?v=k3ECNH1MSCw&fe ature=related

a. Once sister chromatids have split, what are they referred to as?
b. About how long does anaphase of mitosis take?
c. Does each side of the cell have a full set of chromosomes at the end of anaphase?
d. What happens to the mitotic spindle?



Identical nuclear membranes form around each set of chromosomes
Chromosomes start to decondense


Division of cytoplasm
 animal cells
 cleavage furrow
 plant cells
 cell plate

Cleavage furrow in dividing cell
100 µm
Cleavage furrow
Contractile ring of microfilaments
(a) Cleavage of an animal cell (SEM)
Daughter cells

Cell plate in plant cell
Vesicles forming cell plate
Wall of parent cell
Cell plate
1 µm
New cell wall
(b) Cell plate formation in a plant cell (TEM)
Daughter cells

a. Identify the phase in A – D of this photo b. List one feature that tells you the cell in in that particular phase of mitosis
A
C
B D

A plant cell in interphase
Nucleus
Nucleolus
Chromatin condensing
1 Prophase

prophase
Chromosomes
2 Prometaphase

metaphase
3 Metaphase

anaphase
4 Anaphase

Telophase and cytokinesis with cell plate
Cell plate
10 µm
Cell plate
5 Telophase

Onion cells in various stages of the cell cycle

Assignment – read textbook and study slides
Question 10 Fill in the appropriate phase of mitosis or interphase: a.
b.
c.
d.
DNA synthesis occurs : ____
Interphase consists of subphases: ____ ____ ____
Sister chromatids form : ____
Stage that involves a cleavage furrow ____ e.
f.
g.
h.
i.
j.
k.
Beginning of cell cycle ____
Sister chromatids separate ____
The nuclear membrane is visible ____
Chromosomes condense ____
Centromeres line up ____
1 cell divides into two cells ____
A distinct nuclear membrane is visible ____
VIDEOS TO ASSIST YOU next page

 http://www.sumanasinc.com/webcontent/animatio ns/content/mitosis.html
sumanas
 http://www.youtube.com/watch?v=3kpR5RSJ7SA&f eature=related ms stokes bio
 http://www.youtube.com/watch?v=AhgRhXl7w_g pisgahscience
 http://www.johnkyrk.com/mitosis.html
Kyrk

 mitosis is thought to have evolved from binary fission
 Some protists exhibit cell division intermediate between binary fission and mitosis

 The next 2 slides are from the textbook and are summary slides of Interphase G1, S, G2 and M
(mitosis)

G
2 of Interphase
G
2 of Interphase
Centrosomes
(with centriole pairs)
Chromatin
(duplicated)
Prophase
Early mitotic spindle
Prophase
Aster Centromere
Prometaphase
Prometaphase
Fragments of nuclear envelope
Nonkinetochore microtubules
Nucleolus Nuclear envelope
Plasma membrane
Chromosome, consisting of two sister chromatids
Kinetochore Kinetochore microtubule

Metaphase
Metaphase
Metaphase plate
Anaphase
Anaphase
Telophase and Cytokinesis
Telophase and Cytokinesis
Cleavage furrow
Nucleolus forming
Spindle Centrosome at one spindle pole
Daughter chromosomes
Nuclear envelope forming


Short cell cycle– ex. skin cell divides frequently


Longer cycle– ex. brain cell
Mitosis always takes about 40 minutes so the cell cycle differences are in interphase
Cycle completed in 24 hours in skin cell or years in brain cell



 tightly coordinated
checkpoints - cell cycle will not proceed until it checks itself out!
Why does the cell need checkpoints?


Has DNA been copied correctly?
 if there are mutations, they need to be fixed or cell must die!.
Are chromosomes moving correctly?
 during anaphase, a full set of chromosomes must move to the new cells


How is the mitotic spindle?

If its not attaching correctly to chromosomes, they wont move correctly
Is the cell big enough?
 it may need more organelles, membranes etc.

1
The red pieces represent times that the cell meets a checkpoint
The G1 and G2 checkpoints are in interphase
G
1
Control system
M
G
2
S
2



1

0


0

These healthy brain cells are in G o
– they have opted out of the cell cycle, and can stay like this for years

 This is a slide of heart muscle tissue. The cells are in
G o
– they are functioning normally, just not dividing

This is where most cells are, in Go – not dividing, but working normally

 Back to dividing cells and the G1 checkpoint

G
1 checkpoint
G G
0
G G
1
(a) Cell receives a go-ahead signal
G G
1
(b) Cell does not receive a go-ahead signal

The G1 checkpoint – what does it do for the cell?



Ensure that enough nutrients are available to support the new cells
Lets the cell continue in the cell cycle
If the G1 checkpoint is not passed, the cell exits the cell cycle and switches to non-dividing G0 state

Assignment: View the video
 http://www.youtube.com/watch?v=O3_PNiLWBjY
QUESTION 11 a. The restriction point mentioned is the G1 checkpoint. What does the cell do if it does not pass the G1 checkpoint?
b. If the cell passes the G1 checkpoint – what does it commit itself to doing?
c. What is the next cell cycle phase after G2 of interphase?

The G2 checkpoint
 ensures that DNA replication in S phase has been completed successfully.
The M checkpoint
 ensures that all chromosomes are attached to the mitotic spindle.


http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapte r2/animation__control_of_the_cell_cycle.html f.
 a.
b.
c.
d.
e.
QUESTION 12. Fill in the cell cycle stage or cell cycle checkpoint
List the 4 main phases of the cell cycle (do not include the C phase)
What is the name of the phase in which cells that do not pass the G1 checkpoint enter?
If the G1 checkpoint is passed, what then happens to the DNA chromosomes in the cell?
If a cell does not pass the G2 phase, it often self destructs – in what way do you think this is protective for the organism?
What are the 4 sub-phases of mitosis?
Once two new daughter cells are produced (after cytokinesis), which phase of the cell cycle do they each enter?






Format for question submission
1

 a. b.
2

 a. b.
3

 a. b.
4



 a. b. c. d.
 LAST SLIDE NEXT
Follow this pattern for questions 1 – 12. Full sentences only when necessary.

 SUBMIT ANSWERS TO QUESTIONS 1 –12 in an email to blinderl@mccc.edu
by 4 pm Tuesday,
June 21 st .

You will receive a response that your email has been received