Chapter 8: Cell Chapter 8: Cell ReproductionReproduction

ReviewReviewOrganellesOrganelles

CentriolesCentriolesMade of microtubulesMade of microtubulesActs as anchors in cell divisionActs as anchors in cell division

Mitotic Spindle fibersMitotic Spindle fibersTwo Main typesTwo Main types

Kinetochore Fibers- Attach from centriole to Kinetochore Fibers- Attach from centriole to centromere of chromosomes and assists in centromere of chromosomes and assists in movement of chromosomesmovement of chromosomesPolar Fibers – Extend from pole to pole and keep Polar Fibers – Extend from pole to pole and keep the shape of the cell during cell divisionthe shape of the cell during cell division

Nuclear envelopeNuclear envelopeDouble Phospholipid bilayer surrounding nucleusDouble Phospholipid bilayer surrounding nucleusAllows selective passage of RNA and other Allows selective passage of RNA and other materialmaterial

NucleolusNucleolusDense area where DNA is concentrated in the Dense area where DNA is concentrated in the nucleusnucleus

Section 8.1Section 8.1ChromosomesChromosomes

Chromosome StructureChromosome StructureRod-shaped and made of DNA and proteins called Rod-shaped and made of DNA and proteins called histoneshistonesTwo full copies of DNATwo full copies of DNAForm it takes before cell divisionForm it takes before cell divisionHas two identical halves called chromatidHas two identical halves called chromatid

ChromatidChromatidHalf of the chromosomeHalf of the chromosomeOne full copy of DNAOne full copy of DNAAttached in the centerAttached in the center

CentromereCentromereCenter where chromatids areCenter where chromatids areheld togetherheld together

ChromaChromatintinLess tightly coiled DNA-protein complexLess tightly coiled DNA-protein complexTin = thin *Think spaghettiTin = thin *Think spaghettiForm taken during transcriptionForm taken during transcription

Section 8.1Section 8.1Sex ChromosomesSex Chromosomes

Determine gender of the organismDetermine gender of the organismMay carry genes for other characteristicsMay carry genes for other characteristicsEither X or YEither X or YFemale = XX Male = XYFemale = XX Male = XYOne pair (or two chromosomes)One pair (or two chromosomes)

AutosomesAutosomesRemaining chromosomesRemaining chromosomesContain genes for Contain genes for many many traitstraits22 pairs (or 44 chromosomes)22 pairs (or 44 chromosomes)

Section 8.1Section 8.1Homologous ChromosomesHomologous Chromosomes

Two copies of each autosomeTwo copies of each autosomeOne copy from each parentOne copy from each parentSame size and shapeSame size and shapeCarry genes for the same Carry genes for the same traittrait

KaryotypeKaryotypePhotomicrograph of Photomicrograph of chromosomeschromosomesNotice there are 22 pairs of Notice there are 22 pairs of autosomes and 1 pair of sex autosomes and 1 pair of sex chromosomeschromosomesWhat is the gender of this What is the gender of this organism?organism?

Section 8.1Section 8.1DiploidDiploid

Cells that are diploid contain two autosomes Cells that are diploid contain two autosomes from each homologous pair and two sex from each homologous pair and two sex chromosomeschromosomesAbbreviated as Abbreviated as 2n2n

Memory key * di = twoMemory key * di = two

Occurs in all cells except sperm and egg cells Occurs in all cells except sperm and egg cells

HaploidHaploidCells contain only one set of chromosomesCells contain only one set of chromosomesTherefore, half the number of chromosomes Therefore, half the number of chromosomes of a diploid cellof a diploid cellAbbreviated as Abbreviated as 1n1n

Memory key * hap = halfMemory key * hap = half

Sperm cell (Sperm cell (1n1n) and egg cell () and egg cell (1n1n) create a ) create a diploid cell (diploid cell (2n2n))

Section 8.1Section 8.1Notice high Notice high

number of number of chromosomechromosomes in fern s in fern compared to compared to humans!humans!

Section 8.1Section 8.1ActivityActivity

Create a karyotype!Create a karyotype!Arrange in pairs according to length, Arrange in pairs according to length, centromere position, and banding pattern centromere position, and banding pattern

QuestionsQuestions1.1. How many autosomes are there? How many How many autosomes are there? How many

sex chromosomes?sex chromosomes?

2.2. Is the organism a male or female?Is the organism a male or female?

3.3. Why are karyotypes important tools for Why are karyotypes important tools for geneticists?geneticists?

HomeworkHomeworkReview questions on p. 153 #1-5Review questions on p. 153 #1-5

Section 8.1 Review Section 8.1 Review AnswersAnswers

1.1. Name the proteins that DNA wraps around to Name the proteins that DNA wraps around to form a chromosome in eukaryotic cells.form a chromosome in eukaryotic cells.• Histones.Histones.

2.2. How do the structure and location of a How do the structure and location of a prokaryotic chromosome differ from that of a prokaryotic chromosome differ from that of a eukaryotic chromosome?eukaryotic chromosome?• A prokaryotic chromosome consists of a A prokaryotic chromosome consists of a

circular DNA molecule. Eukaryotic circular DNA molecule. Eukaryotic chromosomes are rod-shaped, associated with chromosomes are rod-shaped, associated with histone and nonhistone proteins, and found histone and nonhistone proteins, and found within the cell’s nucleus.within the cell’s nucleus.

3.3. Does chromosome number indicate whether Does chromosome number indicate whether an organism is a plant or animal? Explain.an organism is a plant or animal? Explain.• No. For example, chimpanzees have the same No. For example, chimpanzees have the same

number of chromosomes as potatoes or plums.number of chromosomes as potatoes or plums.

Section 8.1 Review Section 8.1 Review AnswersAnswers

4. Contrast sex chromosomes with autosomes.4. Contrast sex chromosomes with autosomes.• Sex chromosomes determine the gender of Sex chromosomes determine the gender of

an organism. Autosomes are all of the other an organism. Autosomes are all of the other chromosomes in an organism.chromosomes in an organism.

5. Using Table 8-1, list the haploid and diploid 5. Using Table 8-1, list the haploid and diploid number of chromosomes for each organism.number of chromosomes for each organism.

Section 8.1 Review Section 8.1 Review AnswersAnswers

Organism Diploid # Chromosomes Haploid # Chromosomes

Adder’s tongue fern 1262 631

Carrot 18 9

Cat 32 16

Chimpanzee 48 24

Dog 78 39

Earthworm 36 18

Fruit fly 8 4

Garden pea 20 10

Gorilla 48 24

Horse 64 32

Human 46 23

Lettuce 18 9

Orangutan 48 24

Sand dollar 52 26

Section 8.2Section 8.2Cell CycleCell Cycle

Repeating set of events in the life ofRepeating set of events in the life of

a cella cellInterphaseInterphase

Time between cell divisionsTime between cell divisions

Three phasesThree phases

G1 – Cell growthG1 – Cell growth

S – DNA is copiedS – DNA is copied

G2 – Growth and prep for cell divisionG2 – Growth and prep for cell division

Cell divisionCell divisionTwo phasesTwo phases

Mitosis – Nucleus of the cell dividesMitosis – Nucleus of the cell divides

Cytokinesis – Division of the cell’s Cytokinesis – Division of the cell’s cytoplasmcytoplasm

Section 8.2Section 8.2Cell DivisionCell Division

ProkaryotesProkaryotesRemember: Has cell wall, no nuclei, no Remember: Has cell wall, no nuclei, no membrane-bound organellesmembrane-bound organelles

Binary fissionBinary fissionDivision of prokaryotic cell into two offspring Division of prokaryotic cell into two offspring cellscells

Section 8.2Section 8.2Cell Division (cont’d)Cell Division (cont’d)

EukaryotesEukaryotesMitosisMitosis

Division of the nucleusDivision of the nucleus

Four stages (Prophase, Four stages (Prophase, Metaphase, Anaphase, Metaphase, Anaphase, Telophase)Telophase)

CytokinesisCytokinesisIn animal cells, pinching of cellIn animal cells, pinching of cell

membrane occursmembrane occurs

Cleavage furrowCleavage furrow

In plants, cell plate formation In plants, cell plate formation

Section 8.2Section 8.2Control of Cell Control of Cell DivisionDivision

Checkpoints = traffic Checkpoints = traffic signalsignal

Three main Three main checkpointscheckpoints

G1 checkpointG1 checkpoint

G2 checkpointG2 checkpoint

Mitosis checkpointMitosis checkpoint

Section 8.2Section 8.2ActivityActivity

Venn diagram:Venn diagram: Cell division in Prokaryotes Cell division in Prokaryotes vs Eukaryotesvs Eukaryotes

Karyotype Part 2Karyotype Part 2

HomeworkHomeworkCreate the cell cycleCreate the cell cycle

Section 8.2 Section 8.2 (cont’d)(cont’d)

MitosisMitosisProphaseProphase

Tight coiling of DNA into chromosomesTight coiling of DNA into chromosomes

Nucleolus and nuclear membrane break Nucleolus and nuclear membrane break downdown

Centrosomes appear and move to Centrosomes appear and move to opposite ends of the cellopposite ends of the cell

Kinetochore fibers extend from Kinetochore fibers extend from kinetochore from each chromatid to kinetochore from each chromatid to centrosomecentrosome

Metaphase = MiddleMetaphase = MiddleKinetochore fibers move chromosomes to Kinetochore fibers move chromosomes to center of cellcenter of cell

All chromosomes line up in a single file All chromosomes line up in a single file lineline

Section 8.2Section 8.2AnaphaseAnaphase

Chromosomes separate at the Chromosomes separate at the centromere and chromatids move to centromere and chromatids move to opposite polesopposite poles

Chromatids are now considered Chromatids are now considered individual chromosomesindividual chromosomes

TelophaseTelophase

Spindle fibers disassembleSpindle fibers disassemble

Chromosomes return to less tightly Chromosomes return to less tightly coiled chromatin statecoiled chromatin state

Nuclear envelope forms around each set Nuclear envelope forms around each set of chromosomesof chromosomes

Nucleolus forms in each of the newly Nucleolus forms in each of the newly forming cellsforming cells

Animation

Mitosis vs MeiosisMitosis vs MeiosisWhere do they occur?Where do they occur?

Mitosis – in the body cellsMitosis – in the body cellsMeiosis – in the germ cellsMeiosis – in the germ cells

Why does it occur?Why does it occur?MitosisMitosis

Asexual reproductionAsexual reproductionGrowth and developmentGrowth and developmentTo replace old cellsTo replace old cells

MeiosisMeiosisFormation of gametes (egg and sperm cells) Formation of gametes (egg and sperm cells) that will be used in sexual reproductionthat will be used in sexual reproduction

Mitosis vs MeiosisMitosis vs MeiosisEnd result?End result?

46

46 46

MITOSIS

46

23 23

23 23 23 23

MEIOSIS

MeiosisMeiosisAlso known as reduction divisionAlso known as reduction division

Occurs in germ cells found in the ovaries Occurs in germ cells found in the ovaries and testesand testes

Produces sex cells which are haploidProduces sex cells which are haploid

Occurs in two phasesOccurs in two phasesMeiosis IMeiosis I

Reduces the number of chromosomes from Reduces the number of chromosomes from diploid to haploiddiploid to haploid

Meiosis IIMeiosis IIProduces four haploid daughter cellsProduces four haploid daughter cells

Meiosis IMeiosis I

Meiosis IMeiosis IProphase IProphase I

DNA coils tightly into DNA coils tightly into chromosomeschromosomes

Spindle fibers appearSpindle fibers appear

Nucleolus and nuclear Nucleolus and nuclear envelope disassembleenvelope disassemble

Synapsis =Pairing of Synapsis =Pairing of homologous chromosomeshomologous chromosomes

Tetrad =Pair of homologous Tetrad =Pair of homologous chromosomes twisted around chromosomes twisted around each other each other

Crossing over may occurCrossing over may occur

Genetic recombinationGenetic recombination

Meiosis IMeiosis IMetaphase IMetaphase I

Spindle fibers attach to centromere of tetradsSpindle fibers attach to centromere of tetrads

Tetrads line up along midlineTetrads line up along midline

Anaphase IAnaphase IHomologous chromosome pairs are separated Homologous chromosome pairs are separated and move to opposite polesand move to opposite poles

Independent assortment occursIndependent assortment occurs

Telophase ITelophase IChromosomes reach opposite ends of cellChromosomes reach opposite ends of cell

Spindle Fibers disappearSpindle Fibers disappear

Cytokinesis beginsCytokinesis begins

Meiosis IIMeiosis II

Meiosis IIMeiosis IIProphase IIProphase II

Spindle fibers form and attach to the centromeres Spindle fibers form and attach to the centromeres of the double stranded chromosomesof the double stranded chromosomes

Metaphase IIMetaphase IIChromosomes are moved to the midline of the Chromosomes are moved to the midline of the dividing celldividing cell

Anaphase IIAnaphase IIChromatids separate and move toward opposite Chromatids separate and move toward opposite polespoles

Telophase IITelophase IINuclear membrane forms in each of the four new Nuclear membrane forms in each of the four new cellscells

Cytokinesis II occurs resulting in four new cells, Cytokinesis II occurs resulting in four new cells, each with half the original cell’s number of each with half the original cell’s number of chromosomes chromosomes

Section 8.3Section 8.3Results of mitosis vs. meiosisResults of mitosis vs. meiosis

Section 8.3Section 8.3Development Development of Gametesof Gametes

SpermatogenSpermatogenesisesis

OogenesisOogenesis

Polar bodiesPolar bodies

Sexual Sexual reproductionreproduction