Cell ReproductionCell Reproduction

Chapters 9 & 11Chapters 9 & 11

Types of ReproductionTypes of Reproduction

MitosisMitosis

Asexual – only 1 parent needed & the Asexual – only 1 parent needed & the offspring are identical to the parent cell.offspring are identical to the parent cell.

MeiosisMeiosis

Sexual – cells from 2 parents fuse to form Sexual – cells from 2 parents fuse to form new individual. These cells must have ½ new individual. These cells must have ½ the DNA of the parent cells.the DNA of the parent cells.

Cell CycleCell Cycle

G1 – growth phase, most of life spanG1 – growth phase, most of life span

S – DNA synthesis ( 2-4 hrs)S – DNA synthesis ( 2-4 hrs)

G2 – short growth period (4-8 hrs)G2 – short growth period (4-8 hrs)

M – mitosis or meiosis beginsM – mitosis or meiosis begins

G0 – cells that do not divideG0 – cells that do not divide

Cell Cycle

Events of the Cell CycleEvents of the Cell Cycle

MitosisMitosis

Mitosis is division of the nucleusMitosis is division of the nucleus

Cytokinesis is division of the cytoplasmCytokinesis is division of the cytoplasm

Nuclear material is DNANuclear material is DNA

Chromatin – diffuse DNA, spread outChromatin – diffuse DNA, spread out

Chromosomes – coiled DNA, compactChromosomes – coiled DNA, compact

Eukaryotes have pairs of chromosomesEukaryotes have pairs of chromosomes

Figure Figure 9.79.7

Figure 9.7Figure 9.7

figure 09-07.jpg

Phases of MitosisPhases of Mitosis

Interphase Interphase

Non-dividing stage. G1, S, G2Non-dividing stage. G1, S, G2

Cell carries on normal functions.Cell carries on normal functions.

DNA and centrioles are replicated in DNA and centrioles are replicated in preparation for cell division. preparation for cell division.

ProphaseProphase

Chromosomes coil and become compact.Chromosomes coil and become compact.

Chromosomes appear double stranded.Chromosomes appear double stranded.

Chromatids attached at the centromere.Chromatids attached at the centromere.

Centrioles move to the poles.Centrioles move to the poles.

Asters form around centrioles.Asters form around centrioles.

Spindle fibers extend across the cell.Spindle fibers extend across the cell.

Nuclear membrane and nucleolus Nuclear membrane and nucleolus disappear.disappear.

Figure Figure 9.99.9

Figure 9.9Figure 9.9

figure 09-09.jpg

MetaphaseMetaphase

Double stranded chromosomes Double stranded chromosomes individually line up on the equatorindividually line up on the equator

Centromeres attach to a spindle fiberCentromeres attach to a spindle fiber

CENTROMERE

CHROMATIDCENTRIOLE

AnaphaseAnaphase

Chromosomes split & separate Chromosomes split & separate and are pulled to opposite poles and are pulled to opposite poles of the cell by the spindle fibersof the cell by the spindle fibers

TelophaseTelophaseCytoplasm divides (cytokinesis)Cytoplasm divides (cytokinesis)New nuclear membranes formNew nuclear membranes formPlant cells build a new cell wall.Plant cells build a new cell wall.Animal cells pinch in and separate.Animal cells pinch in and separate.

TerminologyTerminology

MitosisMitosis MeiosisMeiosis

AsexualAsexual TypeType SexualSexualDiploidDiploid Chromo.#Chromo.# HaploidHaploid 2n2n n nZygotesZygotes Cell typesCell types GametesGametes

MeiosisMeiosis

There are 2 cell divisions in meiosis.There are 2 cell divisions in meiosis.

Interphase IInterphase I

Chromosomes & centrioles replicateChromosomes & centrioles replicate

Prophase IProphase I

Chromosomes coil and become double Chromosomes coil and become double stranded.stranded.

Centrioles move to the poles.Centrioles move to the poles.

Asters and spindles form.Asters and spindles form.

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

Homologous chromosomes synapse.Homologous chromosomes synapse.

Crossing over occurs. This results in the Crossing over occurs. This results in the creation of variations in the chromosomescreation of variations in the chromosomes

Metaphase IMetaphase I

Chromosomes line up Chromosomes line up in pairsin pairs on the on the equator.equator.

Crossing over continues.Crossing over continues.

Anaphase IAnaphase I

Homologous chromosomes separate and Homologous chromosomes separate and move to opposite poles.move to opposite poles.

Each new cell will receive 1 copy of the Each new cell will receive 1 copy of the original chromosome pairs.original chromosome pairs.

Telophase ITelophase I

Cytokinesis occurs.Cytokinesis occurs.

Each cell has half the number of Each cell has half the number of chromosomes as the original parent cell.chromosomes as the original parent cell.

Chromosomes are still double stranded.Chromosomes are still double stranded.

Interphase IIInterphase II

Chromosomes are uncoiled, but still Chromosomes are uncoiled, but still double stranded.double stranded.

NO DNA replication occurs.NO DNA replication occurs.

Centrioles are replicated.Centrioles are replicated.

Cells contain half the chromosome Cells contain half the chromosome number as the parent cell.number as the parent cell.

Prophase IIProphase II

Same as MitosisSame as Mitosis

Metaphase IIMetaphase II

Same as MitosisSame as Mitosis

Anaphase IIAnaphase II

Same as MitosisSame as Mitosis

Telophase IITelophase II

Same as MitosisSame as Mitosis

Results of MeiosisResults of Meiosis

1 parent cell produces 4 daughter cells1 parent cell produces 4 daughter cells

Daughter cells are haploid gametes.Daughter cells are haploid gametes.

Fertilization results form the fusion of 2 Fertilization results form the fusion of 2 haploid gametes to form a diploid zygote.haploid gametes to form a diploid zygote.

SpermatogenesisSpermatogenesisSperm cell formationSperm cell formation

4 equal sized gametes form4 equal sized gametes form

46D46

23D

23D

23

23

23

23

OogenesisOogenesis

Egg cell formationEgg cell formation

1 large egg + 3 polar bodies (die)1 large egg + 3 polar bodies (die)

46 46D

23D

23D

23

23

23

23

Mitosis vs. MeiosisMitosis vs. Meiosis

23

46

46

23D

23D

23 23 23 23

MeiosisMeiosis

Mitosis

Diploid Cells

FertilizationHaploid

Cells

Gametes

Zygote

Genetic VariationsGenetic VariationsSexual reproduction (fertilization)Sexual reproduction (fertilization)

Meiosis - independent assortment Meiosis - independent assortment

Meiosis - crossing overMeiosis - crossing over

Random MutationsRandom Mutations