8/12/2019 AP Chapter 12 Notes 2
1/41
Chapter 12 notes
The Cell Cycle
8/12/2019 AP Chapter 12 Notes 2
2/41
The Key Roles of Cell DivisionCell division functions in reproduction,
growth, and repairUnicellular organisms (ex. Amoeba) will
divide to reproduce entire organismsCell division also will allows a multicellular
organism to develop from a single cell
8/12/2019 AP Chapter 12 Notes 2
3/41
The Key Roles of Cell DivisionDNA is passed from one generation of
cells to the next without dilution.-cell duplicates it DNA- moves the 2 copies to opposite endsof the cell- and then splits into 2 daughter cells
8/12/2019 AP Chapter 12 Notes 2
4/41
The Key Roles of Cell Division
8/12/2019 AP Chapter 12 Notes 2
5/41
Concept 12.1Cell Division distributes identical sets of
chromosomes to daughter cells A cells genetic material is called its
genome- prokaryote = single long DNA strand- eukaryote = number of DNAmolecules
8/12/2019 AP Chapter 12 Notes 2
6/41
Concept 12.1The replication and distribution of DNA is
manageable because it is packaged intochromosomes- the nuclei in human somatic cells contain 46 chromosomes- the nuclei in human gametes contains 23 chromosomes
8/12/2019 AP Chapter 12 Notes 2
7/41
Concept 12.1
8/12/2019 AP Chapter 12 Notes 2
8/41
Concept 12.1The DNA-protein complex is called the
chromatin and is a long thin fiber. After the chromatin is duplicated, it will
prepare for division. It will condenseand coil up to form chromosomes.
8/12/2019 AP Chapter 12 Notes 2
9/41
Concept 12.1Each duplicated chromosome has 2 sister
chromatids .- each contains identical copies of thechromosomes DNA molecule - they are connected together at thecentromere
8/12/2019 AP Chapter 12 Notes 2
10/41
Concept 12.10.5 m Chromosomes
Chromosomeduplication(including DNAsynthesis)
Chromo-some arm
Centromere
Sisterchromatids
DNA molecules
Separation ofsister chromatids
Centromere
Sister chromatids
8/12/2019 AP Chapter 12 Notes 2
11/41
Concept 12.2The mitotic phase alternates with
interphase in the cell cycleThe mitotic (M) phase (mitosis and
cytokenesis) is the shortest part of thecell cycle.
Interphase accounts for about 90% ofthe cell cycle.
8/12/2019 AP Chapter 12 Notes 2
12/41
Concept 12.2Interphase can be divided into subphases
- G1 (first gap), S (synthesis), and G 2 (second gap)- during subphases, cell grows byproducing proteins and organelles- chromosomes are only duplicatedduring the S phase
8/12/2019 AP Chapter 12 Notes 2
13/41
Concept 12.2
S(DNA synthesis)
G 1
G 2
8/12/2019 AP Chapter 12 Notes 2
14/41
8/12/2019 AP Chapter 12 Notes 2
15/41
Concept 12.2The cell moves into prometaphase
- nuclear envelope fragments- kinetochore attaches to formingspindles- cell prepares for metaphase
8/12/2019 AP Chapter 12 Notes 2
16/41
Concept 12.2
8/12/2019 AP Chapter 12 Notes 2
17/41
Concept 12.2Metaphase
- centrosomes area at opposite poles- chromosomes are on equator of cell,the metaphase plate
Anaphase - begins when the centromeres of thechromosomes separate
8/12/2019 AP Chapter 12 Notes 2
18/41
Concept 12.2- sister chromatids begin movingtoward opposite poles- by the end, the poles have equal setsof chromosomes
Telophase- daughter nuclei form at the poles- nuclear envelope begins to reform
8/12/2019 AP Chapter 12 Notes 2
19/41
Concept 12.2- chromosomes become less tightly
coiled-Cytokenesis, the division of the
cytoplasm, follows immediately
8/12/2019 AP Chapter 12 Notes 2
20/41
Concept 12.2
8/12/2019 AP Chapter 12 Notes 2
21/41
Concept 12.2The mitotic spindle distributes
chromosomes to the daughter cells-during interphase, the singlecentrosome replicates to form 2centrosomes; during the early stage of
mitosis, they separate and move towardopposite poles helping the spindle fibers
8/12/2019 AP Chapter 12 Notes 2
22/41
Concept 12.2
8/12/2019 AP Chapter 12 Notes 2
23/41
Concept 12.2Cytokenesis divides the cytoplasm
- in animals, cytokenesis occurs by theformation of a cleavage furrow- in plants the cleavage cannot occurbecause of the cell wall; vesicles willmove to the center of the cell to formthe cell plate .
8/12/2019 AP Chapter 12 Notes 2
24/41
Concept 12.2
Cleavage furrow100 m
Contractile ring ofmicrofilaments
Daughter cells
(a) Cleavage of an animal cell (SEM) (b) Cell plate formation in a plant cell (TEM)
Vesiclesformingcell plate
Wall ofparent cell
Cell plate
Daughter cells
New cell wall
1 m
8/12/2019 AP Chapter 12 Notes 2
25/41
Concept 12.2The origins of mitosis are believed to be from
bacterial organisms of cell reproduction- prokaryotes reproduce by binary fission(dividing in half) - prokaryotes do not have mitotic spindles;instead, once the DNA replicates, the copies ofthe region move apart rapidly
8/12/2019 AP Chapter 12 Notes 2
26/41
Concept 12.2Origin ofreplication
Two copies
of origin
E . c o l i cell Bacterialchromosome
Plasmamembrane
Cell wall
Origin Origin
8/12/2019 AP Chapter 12 Notes 2
27/41
Concept 12.3The cell cycle is driven by specific chemical
signals present in the cytoplasmSequential events of the cell cycle are directed
by a distinct cell cycle control system - driven by a built in clock- the cell cycle is regulated at certaincheckpoints by internal and external controls
8/12/2019 AP Chapter 12 Notes 2
28/41
Concept 12.3
8/12/2019 AP Chapter 12 Notes 2
29/41
The checkpoint is a control point wherestop and go-ahead signals can regulatethe cycle- kinases, a type of regulatory proteinthat activate or inactivate other
proteins, give the signals for G 1 and G 2 checkpoints
Concept 12.3
8/12/2019 AP Chapter 12 Notes 2
30/41
Concept 12.3To be active the kinase must be attached
to a cyclin (kinases become cyclin-
dependent kinases or Cdks )- the activity of Cdks rises and falls withchanges in the [cyclin]
- first called MPF = maturationpromoting factor or M -phase-promoting factor
8/12/2019 AP Chapter 12 Notes 2
31/41
Concept 12.3- when cyclins accumulate during G 2,MPF initiates mitosis
Internal and external cues help regulatethe cell cycle- for cells to divide a growth factor, aspecific protein, is released to stimulatecell division
8/12/2019 AP Chapter 12 Notes 2
32/41
8/12/2019 AP Chapter 12 Notes 2
33/41
Concept 12.3The discovery of growth factors has led
us to understand density-dependentinhibition of cell division- when a cell population reaches acertain density, the amount of growth
factors and nutrients needed fordivision becomes insufficient forincreased growth
8/12/2019 AP Chapter 12 Notes 2
34/41
8/12/2019 AP Chapter 12 Notes 2
35/41
Concept 12.3
Anchorage dependence
Density-dependent inhibition
Density-dependent inhibition
(a) Normal mammalian cells (b) Cancer cells25 m25 m
8/12/2019 AP Chapter 12 Notes 2
36/41
Concept 12.3
8/12/2019 AP Chapter 12 Notes 2
37/41
8/12/2019 AP Chapter 12 Notes 2
38/41
Concept 12.3- if cancer cells stop dividing, it is atrandom points and not at the
checkpointsCaner begins when a single cell tissue
undergoes a transformation
- if the cell evades destruction by theimmune system it may form a tumor
8/12/2019 AP Chapter 12 Notes 2
39/41
Concept 12.3- if the abnormal cell remain at theoriginal site, it is called a benign
tumor- a malignant tumor becomesinvasive enough to impair the functionsof organs- the spread of cancer cells from theoriginal site is called metastasis
8/12/2019 AP Chapter 12 Notes 2
40/41
8/12/2019 AP Chapter 12 Notes 2
41/41
Concept 12.3