CELL CYCLE

Mitosis

The functions of cell division: Reproduction

The functions of cell division: Growth and development

Eukaryotic Chromosomes

The functions of cell division: Growth and development

Mitosis

• The form of cell divisioncell division by which a eukaryotic somatic cellsomatic cell duplicates.

• MitosisMitosis is asexual reproductionasexual reproduction..

• Cell divisionCell division is the continuation of life based on the reproduction of cells.

MitosisMitosis

2n=46

Skin Cell 2n=46

2n=46

twoidenticaldaughtercells

Skin Cell

Skin Cell

The Asexual Reproduction of a Hydra

Budding

Somatic ReproductionSomatic Reproduction• Most eukaryotic cells reproduce

asexually by mitosismitosis.

• Somatic cellsSomatic cells are all body cellsbody cells (like nerve, liver, etc...) (like nerve, liver, etc...) except sperm and ova (egg).

• All somatic cells have the same number of chromosomeschromosomes.

Cell CycleCell Cycle

Mitosis-prophase-metaphase-anaphase-telophase

G1 G2

Sphase

interphase

Cell CycleCell Cycle• The dividingdividing and non-dividingnon-dividing

stages in the life of a cell.• Phases:

1.1. InterphaseInterphase: growth and DNA replication2.2. ProphaseProphase3.3. MetaphaseMetaphase4.4. AnaphaseAnaphase5.5. TelophaseTelophase

Mitotic divisionMitotic division

Molecular Control of the Cell Cycle at the G2 Checkpoint

InterphaseInterphase• Comprises about 90%90% of the cell cell

cyclecycle.• Cellular growthCellular growth:

a. protein synthesisprotein synthesisb. metabolic activitiesmetabolic activitiesc. DNADNA synthesissynthesis

• Made up of three phasesthree phases:

1. G1. G11 phase phase

2. S phase2. S phase

3. G3. G22 phase phase

InterphaseInterphase

1. 1. GG11 (gap) phase: (gap) phase:

a. Cellular growth, protein synthesis and metabolic activities.

2. S phase:2. S phase:

a. DNA DNA synthesis/synthesis/replication replication takes place.

3.3. GG22 (gap) phase: (gap) phase:

a. organelles replicated, chromosomes condense, microtubules assemble

b. Preparation for M phaseM phase.

InterphaseInterphase

• NucleusNucleus and nucleolusnucleolus visible.

Nuclear membrane

nucleolus

cell membrane

chromatin

QuestionQuestion::

• What is a chromosome?What is a chromosome?

Answer:Answer:• A chromosomechromosome is made up of

a DNADNA - histone proteinhistone protein complex called chromatinchromatin.

ChromatinChromatin is a long, thin fiber that is folded and coiled to form chromosomeschromosomes. DNA double helix

Histone proteins

chromosome

Question:Question:

• What is a replicated What is a replicated chromosomechromosome??

Answer:Answer:• A replicated chromosomechromosome consist

of two strands of identical chromosomal material called chromatidschromatids (sister chromatidssister chromatids).

chromatid

chromatid

S phase: chromosomes replicate

chromosome

chromosome

centromere

Chromosome Duplication and Distribution During Mitosis

Question:Question:

• When is a When is a chromatidchromatid a a chromatidchromatid??

• A chromatidchromatid is a chromatidchromatid as long as it is held in association with a sistersister chromatidchromatid at the centromerecentromere.

chromatid

centromere

chromosome

Chromatid

Mitotic PhaseMitotic Phase• Mitosis Mitosis

a. nuclearnuclear division of genetic genetic materialmaterial.b. prophase-metaphase-b. prophase-metaphase-anaphase-telophaseanaphase-telophase

• CytokinesisCytokinesisa.a. cytoplasmic divisioncytoplasmic division.b. Indicator of telophase.

The stages of mitotic cell division in an animal cell: G2 phase; prophase; prometaphase

The stages of mitotic cell division in an animal cell: metaphase; anaphase; telophase and cytokinesis.

The Cell Cycle and Mitosis

ProphaseProphase

• Longest phaseLongest phase

• Nucleolus disappears

• Chromatin material condenses into chromosomeschromosomes, consisting of two sister chromatidssister chromatids.

ProphaseProphase• CentriolesCentrioles move apart (not found

in plants).

• Spindle fibers Spindle fibers form and attach from centriolescentrioles to centromerescentromeres by kinetochoresby kinetochores..

• Nuclear envelope fragments and disappears.

ProphaseProphase

late prophaselate prophaseearly prophaseearly prophase

centrioles

spindle fibers

centromere

nuclear envelopedisappearing

asterfibers

Question:Question:

• What attaches the What attaches the spindle spindle fibersfibers to the to the centromerescentromeres??

Answer:Answer: Kinetochores Kinetochores

sistersisterchromatidchromatid

sistersisterchromatidchromatid

centromerecentromere

spindle fiberspindle fiber kinetochoreskinetochores

centriole

asterfibers

MetaphaseMetaphase• Shortest phase

• CentriolesCentrioles are at opposite ends of the cell and attached with aster fibersaster fibers.

• ChromosomesChromosomes move to the metaphase platemetaphase plate (equatorial equatorial plateplate - center of cell).

MetaphaseMetaphase

metaphase plate

centrioles

spindle fibers

asterfibers

Metaphase

Karyotypes Karyotypes are typically made are typically made during during metaphasemetaphase. .

• A method of organizing the chromosomes of a A method of organizing the chromosomes of a cell in relation to number, size, and type.cell in relation to number, size, and type.

AnaphaseAnaphase• CentromeresCentromeres uncouple and

spindle fibers spindle fibers shorten.

• Sister chromatids Sister chromatids separate and move apart.

• After separation, chromatidschromatids are now considered chromosomeschromosomes.

AnaphaseAnaphase

• During this phase, the cell contains twice the normal number of chromosomeschromosomes.

• Cell begins to elongateelongate.

• At the end, there are equal numbers of chromosomeschromosomes at the poles.

AnaphaseAnaphase

No longer sister chromatidssister chromatids, now chromosomeschromosomes

centriolesspindle fibers

asterfibers

TelophaseTelophase• Cleavage furrowfurrow develops in

animal cells (CytokinesisCytokinesis begins).

• Cell plate develops in plantsplants (no cleavage furrows in plants).

• Nucleolus reappears.

cell plate

TelophaseTelophase

• Nuclear membrane reappears.

• ChromosomesChromosomes uncoil.

• In the end, two genetically identical nuclei (karyokinesiskaryokinesis completed) are present.

TelophaseTelophase

cleavage furrow (cytokinesis)

nuclear membrane reforming nucleolus reappears

CytokinesisCytokinesis• Cytoplasmic divisionCytoplasmic division

• Cell plateCell plate complete in plantsplants

• In the end, two separate daughter cells produced with single nucleus.

cell plate

Cytokinesis in Animal and Plant Cells

A Hypothesis for the Evolution of Mitosis

microtubulesform spindlewithin nucleus

Bacterial Cell Division (binary fission)

Mitosis in a Plant Cell

Mitosis in an Onion Root

Question:Question:

• A cell containing 2020 chromosomeschromosomes at the beginning of mitosis would, at its completion, produce cells containing how many chromosomes eachchromosomes each?

Answer:Answer:

• 20 chromosomes20 chromosomes

Question:Question:

• A cell containing 4040 chromatidschromatids at the beginning of mitosis would, at its completion, produce cells containing how many chromosomes eachchromosomes each?

Answer:Answer:

• 20 chromosomes20 chromosomes

Density-Dependent Inhibition of Cell Division

The Growth and Metastasis of a Malignant Breast Tumor

Breast Cancer Cell

Mammogram: Normal (left) and Cancerous (rt)

Cancer Cells

Cancer Cells Versus Normal Cells

1)Give two reasons why cells divide.

2) As a cell increases in size, whichincreases more rapidly, its surface area or its volume?

Draw a chromosome and labelthe chromatids and centromere.

The division of the cytoplasm at the end of mitosis is called: