The Cell CycleThe Cell Cycle

Why do cells divide? Why do cells divide?

For growth and repairFor growth and repair To get food, water, and waste in and To get food, water, and waste in and

out of our bodies quicklyout of our bodies quickly

What is the Cell Cycle?What is the Cell Cycle?

Series of events that take place from Series of events that take place from one cell division to the nextone cell division to the next

Constantly repeatedConstantly repeated

Three Stages of the Cell Three Stages of the Cell CycleCycle

InterphaseInterphase Mitosis Mitosis CytokinesisCytokinesis

InterphaseInterphase

Period of growth Period of growth and developmentand development

Longest phase of Longest phase of the cell cyclethe cell cycle

Some cells never Some cells never leave interphase leave interphase such as nerve and such as nerve and muscle cellsmuscle cells

What happens during What happens during interphase?interphase?

Cell grows in size; Cell grows in size;

makes an extra set of makes an extra set of structuresstructures

Cell makes a copy of Cell makes a copy of its hereditary its hereditary material. (DNA)material. (DNA)

Produces structures Produces structures needed for division needed for division (spindle fibers, (spindle fibers, centrioles)centrioles)

DNADNA

Deoxyribonucleic acidDeoxyribonucleic acid It is our hereditary material (passed It is our hereditary material (passed

on from our parents)on from our parents) Found in the nucleus of our cells as Found in the nucleus of our cells as

chromatinchromatin

Chromatin vs. Chromatin vs. ChromosomesChromosomes

Chromatin is Chromatin is uncoiled DNAuncoiled DNA

Chromosomes are Chromosomes are tightly coiled tightly coiled strands of DNAstrands of DNA

ChromosomesChromosomes

ChromosomesChromosomes

Humans have 46 Humans have 46 chromosomes in chromosomes in each of their cellseach of their cells

Human KaryotypeHuman Karyotype

Chromosome #’sChromosome #’s

Carrot-18 Carrot-18 Cat- 32Cat- 32 Dog-78Dog-78 Earthworm-36Earthworm-36 Fruit fly-8Fruit fly-8 Chimpanzee-48Chimpanzee-48 Adder’s tongue fern-1,262Adder’s tongue fern-1,262

MitosisMitosis

Is the division of the nucleusIs the division of the nucleus Results in two new identical nucleiResults in two new identical nuclei

Four Stages of MitosisFour Stages of Mitosis

ProphaseProphase MetaphaseMetaphase AnaphaseAnaphase TelophaseTelophase

ProphaseProphase

Duplicated Duplicated chromosomes chromosomes become visiblebecome visible

Nucleolus and Nucleolus and nuclear membrane nuclear membrane disappear.disappear.

Centrioles move to Centrioles move to opposite ends of the opposite ends of the cellcell

Spindle fibers stretch Spindle fibers stretch across the cellacross the cell

MetaphaseMetaphase

Duplicated Duplicated chromosomes line chromosomes line up across the up across the center of the cell.center of the cell.

Centromeres Centromeres attach to spindle attach to spindle fibers.fibers.

AnaphaseAnaphase

Centromeres Centromeres dividedivide

Identical Identical chromosomes chromosomes separate and move separate and move to opposite ends of to opposite ends of the cellthe cell

Cell begins to Cell begins to stretchstretch

TelophaseTelophase

Spindle fibers Spindle fibers disappeardisappear

Chromosomes uncoilChromosomes uncoil New nuclear New nuclear

membrane forms membrane forms around each region around each region of chromosomes.of chromosomes.

A new nucleolus A new nucleolus forms in each new forms in each new nucleus. nucleus.

CytokinesisCytokinesis

The division of the cytoplasmThe division of the cytoplasm Usually starts around the same time Usually starts around the same time

as telophaseas telophase Results in two new identical cells Results in two new identical cells

(daughter cells) that have the same (daughter cells) that have the same # of chromosomes as the original # of chromosomes as the original parent cellparent cell

Cytokinesis in Animal Cytokinesis in Animal CellsCells

Cell membrane Cell membrane pinches together pinches together around the middle around the middle of the cell creating of the cell creating two new cellstwo new cells

Each daughter cell Each daughter cell gets about half of gets about half of the organellesthe organelles

Cytokinesis in Plant cellsCytokinesis in Plant cells

Cell plate forms Cell plate forms down the center of down the center of the cellthe cell

The cell plate The cell plate gradually develops gradually develops into a cell into a cell membrane membrane

New cell walls New cell walls form around the form around the cell membranecell membrane

Cell CycleCell Cycle

Prophase

Metaphase

AnaphaseTelophase

Cytokinesis

Interphase

Asexual ReproductionAsexual Reproduction

Produces a new organism that has Produces a new organism that has identical hereditary material to the identical hereditary material to the parent.parent.

Involves only one parent.Involves only one parent.

3 Types of Asexual 3 Types of Asexual ReproductionReproduction

1. Fission1. Fission 2. Budding2. Budding 3. Regeneration3. Regeneration

FissionFission

Simplest form of reproductionSimplest form of reproduction Used by one celled organisms such as Used by one celled organisms such as

bacteriabacteria Cell grows in size, makes a copy of its Cell grows in size, makes a copy of its

hereditary material, and divides to hereditary material, and divides to make two new identical daughter make two new identical daughter cells.cells.

Daughter cells are usually smaller Daughter cells are usually smaller than parentthan parent

BuddingBudding

Process by which Process by which organisms, such as organisms, such as yeast, form a tiny yeast, form a tiny bud that grows out bud that grows out and breaks off of and breaks off of the parent cell the parent cell when it is large when it is large enough.enough.

New cell may be New cell may be smaller than parentsmaller than parent

RegenerationRegeneration

Ability of an organism to regrow lost Ability of an organism to regrow lost or damaged body parts.or damaged body parts.

May result in whole new organism.May result in whole new organism. Examples: lizard’s tail, starfishExamples: lizard’s tail, starfish

StarfishStarfish PlanariaPlanaria