CHAPTER 12 The Cell Cycle. The Key Roles of Cell Division cell division = reproduction of cells All...
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CHAPTER 12 The Cell Cycle
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Transcript of CHAPTER 12 The Cell Cycle. The Key Roles of Cell Division cell division = reproduction of cells All...
CHAPTER 12
The Cell Cycle
The Key Roles of Cell Division
cell division = reproduction of cellsAll cells come from pre-exisiting cells
Omnis cellula e cellula
Unicellular organisms division of 1 cell reproduces organism
Binary fission
Why cells reproduce Development/Growth Replacement Repair
Multicellular organisms
100 µm 200 µm 20 µm
(a) Reproduction (b) Growth and development
(c) Tissue renewal
Cellular Organization of Genetic Material
chromosome = strand of DNA 2 sets of 23 chromosomes in humans = 46
genome = All DNA in a cell
20 µm
chromatin complex of DNA and protein
Somatic cells= body cells (2 trillion in adult) two sets of chromosomes (pairs= diploid) Produced by mitosis - 1 diploid cell 2 identical
diploid cells
Gametes sperm and eggs have 1 set = haploid Produced by meiosis– 1 diploid cell 4 unique cells Occurs only in ?
Identical cells Unique cellsDiploid Haploid
Concept check
1. start with a fertilized egg 5 cell divisions produce how an embryo of ______ cells
2. a chicken has 78 chromosomes in a somatic cell. How many chromosomes in a chicken sperm?
Human Arabidposis
The cell cycle = time from new cell to when it divides
Interphase – 90% of time
Mitosis 4o min
S(DNA synthesis)
MITOTIC(M) PHASE
G1
G2
Cell Division
Mitosis = division of the nucleusCytokinesis = division of cytoplasm
INTERPHASEG1 phase – cell grows, gets readyS phase – DNA replicatesG2 phase – cell grows, gets ready
S(DNA synthesis)
MITOTIC(M) PHASE
G1
G2
If cycle is 24 hrs, how longeach phase?
Signs of interphase?
S phase of Interphase
Chromosomes (DNA) replicate
Sister chromatids = 2
Centromere = constricted region
0.5 µm Chromosomes
Chromosomeduplication(including DNAsynthesis)
Chromosome arm
Centromere
Sisterchromatids
DNA molecules
Separation ofsister chromatids
Centromere
Sister chromatids
Prophase Prometaphase Metaphase Anaphase Telophase
Cytokinesis by late telophase
MITOSIS video
Chromosomes condense Mitotic spindle forms from centrioles Nuclear membrane breaks apart
I. Prophase
The mitotic spindle (formation begins in prophase)
Prophase G2 of Interphase
AsterCentrosomes
Aster = radial array of microtubules
Prophase
II. Prometaphase
Spindle microtubules attach to kinetochores of chromosomes Chromosomes pulled towards center of cell
III. Metaphase
chromosomes (sister chromatids) line up at the metaphase plate
midway between spindle’s two poles
MicrotubulesChromosomes
Sisterchromatids
Aster
Metaphaseplate
Centrosome
Kineto-chores
Kinetochoremicrotubules
Overlappingnonkinetochoremicrotubules
Centrosome1 µm
0.5 µm
Prophase PrometaphaseG2 of Interphase
PrometaphaseProphaseG2 of Interphase
Nonkinetochoremicrotubules
Fragmentsof 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
IV. Anaphase
sister chromatids separate
microtubules shorten – depolymerize to move chromosomes toward opposite ends of cell
V. Telophase
Identical nuclei form at opposite ends of cellChromosomes less condensed
Cytokinesis
Division of cytoplasmanimal cells
cleavage furrow
plant cells cell plate
Cleavage furrow100 µm
Daughter cells
(a) Cleavage of an animal cell (SEM)
Contractile ring ofmicrofilaments
Daughter cells
(b) Cell plate formation in a plant cell (TEM)
Vesiclesformingcell plate
Wall ofparent cell
New cell wallCell plate
1 µm
Nucleus
Prophase1
NucleolusChromatincondensing
Prometaphase2
Chromosomes
Metaphase3
Anaphase4
Telophase5
Cell plate10 µm
Evolution of Mitosis
mitosis is thought to have evolved from binary fission
Some protists exhibit cell division intermediate between binary fission and mitosis
The cell cycle is regulated by a molecular controls
Short length – ex. skin cell Longer length – ex. Neurons
Specific signal molecules in cytoplasm
SG1
M checkpoint
G2M
Controlsystem
G1 checkpoint
G2 checkpoint
Application: Cancer
Mutation in cell cycle genes
Breast cancer cells dividing
