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The Cell Cycle. Chapter 12 VIEW SLIDES> TAKE NOTES TO ORGANIZE AND LEARN THE INFORMATION ALL SLIDES, INFO FROM VIDEOS and question topics will be on exam #3 COMPLETE QUESTIONS FOR EACH SECTION. SEND THE COMPLETED QUESTIONS by Monday Nov 7 to - PowerPoint PPT Presentation
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CHAPTER 12
VIEW SLIDES> TAKE NOTES TO ORGANIZE AND LEARN THE INFORMATION ALL SLIDES, INFO FROM VIDEOS AND QUESTION TOPICS WILL BE ON EXAM #3
COMPLETE QUESTIONS FOR EACH SECTION. SEND THE COMPLETED QUESTIONS BY MONDAY NOV 7 TO
WORK SUBMITTED MUST BE IN THE STUDENTS OWN WORDS
The Cell Cycle
READ CHAPTER 12 IN TEXTBOOK
The Key Roles of Cell Division
cell division = reproduction of cellsAll 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
ASSIGNMENT: View video on binary fission http://www.youtube.com/watch?v=J6akNYlkehY
QUESTION 1: a.How frequently do some bacteria divide?b.How does this explain their ability to expand their numbers quickly?
Why cells reproduce Development/Growth
Replacement
Repair
Multicellular organisms
Example: embryo adult
Example: stomach lining iscontinually replaced
Example: repair of burn
Watch the videohttp://www.youtube.com/watch?v=f7cXeWxxf
D4
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)
Cellular Organization of Genetic Material
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)
Assignment: View the data on the website http://morgan.rutgers.edu/morganwebframes/level1/page2/ChromNum.html Explore the number of chromosomes in each type of organism’s cells.
Question 2: a. Is there a correlation between chromosome number and
intelligence? Provide evidence to support your claim.
20 µm
This is an electron micrograph of the46 chromosomes in a human cell.
chromatin complex of DNA and protein
20 µmChromatin normally looksdiffuse - hard to see individual chromosomes
Terms needed to continue
Haploid – a cell with one set of chromosomesDiploid – a cell with two sets of chromosomes
Assignment. Visit the website http://www.ncbi.nlm.nih.gov/books/NBK9863/
Question 3 a. Look carefully at the list – are these diploid, or haploid
chromosome numbers?b. How many chromosomes are in the sperm of a fruit fly?c. 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 Unique cellsDiploid Haploid
Assignment: Read the textbook and study the previous slides to answer the followingQUESTION 4a.A fruit fly sperm contains 4 chromosomes. How many chromosomes . Which of the cells below are diploid? (there are 6)
- fruit fly wing cell - monkey liver cell- haploid cell - plant pollen (contains sperm)- gamete from a fern plant - fish somatic cell- fertilized whale egg- human embryo cell- cell produced by meiosis - cell with 2 sets of chromosomes- sperm of frog - unfertilized bird egg
b. Which of the following terms are associated with mitosis (there are 6)
- sperm - somatic - genetically identical- diploid - ovary - 2n- unique cells - liver cell - 46 chromosomes- 1 set of chromosomes - 4 daughter cells - gametes
Cell Division also includes:
Nuclear division= division of the nucleusCytokinesis = division of cytoplasm
View the video to comparehttp://www.youtube.com/watch?v=rgLJrvoX_qo&NR=1
When both have occurred, there are 2 new cells, each identical to the “parent” cell
The cell cycle = time from new cell to when it divides
Interphase ~ 90% of a cell’s timecell is doing its normal activity during this time
Mitosis - ~ 4o mincell is involved in replicating to make 2 new cells
S(DNA synthesis)
MITOTIC(M) PHASE
G1
G2
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 readyS phase – DNA replicatesG2 phase – cell grows, gets ready
S(DNA synthesis)
MITOTIC(M) PHASE
G1
G2
Watch the cell cycle videohttp://www.youtube.com/watch?v=O3_PNiLWBjY
Signs of interphase?Note the distinct nuclear membraneNote 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
S phase of InterphaseChromosomes 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
Assignment: review the textbook and notesQuestion 5a)Number of chromosomes in a human sperm or egg cellb)Number of chromosomes in a human fertilized eggc)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
PHASES OF MITOSIS
A. Chromosomes condense = they become thicker and shorterB. Nuclear membrane breaks apartC. Mitotic spindle forms from centrioles
I. Prophase of Mitosis
WATCH THE PROPHASE VIDEOhttp://www.youtube.com/watch?v=BFDSlHv3SZU
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
Prophase of mitosisThis 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
The mitotic spindle in prophase
Remember the centriolesThey 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/spindle-fibers-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. Question 6a.Are the two sister chromatids that compose a chromosome in prophase identical?b.To what structure do the mitotic spindle microtubules attach on the chromosomes?c.What are the components of the mitotic spindle?d.What are centrioles composed of?e.What is meant by “chromosomes condense” ?
WATCH THE PROPHASE VIDEOhttp://www.youtube.com/watch?v=BFDSlHv3SZU
II. Metaphase of mitosis
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
The chromosomes here do not look as neat – but their centromeres are in a line on the metaphase plate
Metaphase plate
Centriole with spindle fibers
Assignment: Watch the metaphase video
http://www.youtube.com/watch?v=8C7Y1F1uyQs&feature=related
Question 7a.How can you determine visually that a cell is in metaphase?b. About how long in minutes or hours is metaphase?c.Is the spindle apparatus (mitotic spindle) obvious during metaphase?d.Are the sister chromatids still attached at the centromere during metaphase?
III. Anaphase 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
Assignment: Watch the anaphase videohttp://www.youtube.com/watch?v=k3ECNH1MSCw&feature=related
Question 8a. 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?
IV. Telophase of mitosis
Identical nuclear membranes form around each set of chromosomes
Chromosomes start to decondense
CytokinesisDivision of cytoplasmanimal cells
cleavage furrow
plant cells cell plate
Cleavage furrow100 µm
Daughter cells
(a) Cleavage of an animal cell (SEM)
Contractile ring ofmicrofilaments
Cleavage furrow in dividing cell
Daughter cells
(b) Cell plate formation in a plant cell (TEM)
Vesiclesformingcell plate
Wall ofparent cell
New cell wallCell plate
1 µm
Cell plate in plant cell
Assignment: Read textbook and study slides
Question 9 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 CA
B D
Nucleus
Prophase1
NucleolusChromatincondensing
A plant cell in interphase
Prometaphase2
Chromosomes
prophase
Metaphase3
metaphase
Anaphase4
anaphase
Telophase5
Cell plate 10 µmTelophase and cytokinesis with cell plate
Cell plate
Onion cells in various stages of the cell cycle
Assignment – read textbook and study slidesQuestion 10 Fill in the appropriate phase of mitosis or interphase:
a. DNA synthesis occurs : ____b. Interphase consists of subphases: ____ ____ ____c. Sister chromatids form : ____d. Stage that involves a cleavage furrow ____e. Beginning of cell cycle ____f. Sister chromatids separate ____g. The nuclear membrane is visible ____h. Chromosomes condense ____i. Centromeres line up ____j. 1 cell divides into two cells ____k. A distinct nuclear membrane is visible ____VIDEOS TO ASSIST YOU next page
http://www.sumanasinc.com/webcontent/animations/content/mitosis.html sumanas
http://www.youtube.com/watch?v=3kpR5RSJ7SA&feature=related ms stokes bio
http://www.youtube.com/watch?v=AhgRhXl7w_gpisgahscience
http://www.johnkyrk.com/mitosis.html Kyrk
Evolution of Mitosismitosis 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)
Prophase PrometaphaseG2 of Interphase
PrometaphaseProphaseG2 of InterphaseNonkinetochore
microtubulesFragmentsof nuclearenvelope
Aster CentromereEarly mitoticspindle
Chromatin(duplicated)
Centrosomes(with centriolepairs)
Nucleolus Nuclearenvelope
Plasmamembrane
Chromosome, consistingof two sister chromatids
Kinetochore Kinetochoremicrotubule
Metaphase Anaphase Telophase and Cytokinesis
Metaphase Anaphase Telophase and Cytokinesis
Cleavagefurrow
Nucleolusforming
Metaphaseplate
Centrosome atone spindle pole
SpindleDaughterchromosomes
Nuclearenvelopeforming
The cell cycle is regulated by molecular controls
Short cell cycle– ex. skin cell divides frequently
Longer cycle– ex. brain cellMitosis always takes about 40 minutes so the
cell cycle differences are in interphase
Cycle completed in 24 hours or years in brain cellin skin cell
tightly coordinatedcheckpoints - 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.
Cell cycle control
SG1
M checkpoint
G2M
Controlsystem
G1 checkpoint
G2 checkpoint
The red pieces represent times that the cell meets a checkpoint
The G1 and G2 checkpoints are in interphase
G1 checkpoint (interphase) most important If no “go” signal, cell will move to an
opt out phase called G0 phase (non-dividing) Most cells are in G0
Can re-enter cell cycle
These healthy brain cells are in Go – 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 Go – 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
G1
G0
(a) Cell receives a go-ahead signal
G1
(b) Cell does not receive a go-ahead signal
G1
G0
G1 checkpoint
(a) Cell receives a go-ahead signal
G1
(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 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_PNiLWBjYQUESTION 11a. 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 checkpointensures that DNA replication in S phase has
been completed successfully.
The M checkpointensures that all chromosomes are attached to
the mitotic spindle.
Last assignment: View the video http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__control_of_the_cell_cycle.html
QUESTION 12. Fill in the cell cycle stage or cell cycle checkpoint
a. List the 4 main phases of the cell cycle (do not include the C phase)
b. What is the name of the phase in which cells that do not pass the G1 checkpoint enter?
c. If the G1 checkpoint is passed, what then happens to the DNA chromosomes in the cell?
d. 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?
e. What are the 4 sub-phases of mitosis?f. 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.
Follow this pattern for questions 1 – 12. Full sentences only when necessary.
LAST SLIDE NEXT
SUBMIT ANSWERS TO QUESTIONS 1 –12 in an email to [email protected] by 11:59 pm Monday Nov 7th.
You will receive a response that your email has been received