Review Organelles Centrioles Made of microtubules Acts as anchors in cell division Mitotic Spindle fibers Two Main types Kinetochore Fibers Attach from centriole to centromere of chromosomes and assists in movement of chromosomes ID: 265677
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Slide1
Chapter 8: Cell ReproductionSlide2
Review
Organelles
CentriolesMade of microtubulesActs as anchors in cell divisionMitotic Spindle fibersTwo Main typesKinetochore Fibers- Attach from centriole to centromere of chromosomes and assists in movement of chromosomesPolar Fibers – Extend from pole to pole and keep the shape of the cell during cell divisionNuclear envelopeDouble Phospholipid bilayer surrounding nucleusAllows selective passage of RNA and other materialNucleolusDense area where DNA is concentrated in the nucleusSlide3
Section 8.1
Chromosomes
Chromosome StructureRod-shaped and made of DNA and proteins called histonesTwo full copies of DNAForm it takes before cell divisionHas two identical halves called chromatidChromatidHalf of the chromosomeOne full copy of DNAAttached in the centerCentromere
Center where chromatids are
held together
ChromatinLess tightly coiled DNA-protein complexTin = thin *Think spaghettiForm taken during transcriptionSlide4
Section 8.1
Sex Chromosomes
Determine gender of the organismMay carry genes for other characteristicsEither X or YFemale = XX Male = XYOne pair (or two chromosomes)AutosomesRemaining chromosomesContain genes for many traits22 pairs (or 44 chromosomes)Slide5
Section 8.1
Homologous Chromosomes
Two copies of each autosomeOne copy from each parentSame size and shapeCarry genes for the same traitKaryotypePhotomicrograph of chromosomesNotice there are 22 pairs of autosomes and 1 pair of sex chromosomesWhat is the gender of this organism?Slide6
Section 8.1
Diploid
Cells that are diploid contain two autosomes from each homologous pair and two sex chromosomesAbbreviated as 2nMemory key * di = twoOccurs in all cells except sperm and egg cells HaploidCells contain only one set of chromosomesTherefore, half the number of chromosomes of a diploid cellAbbreviated as 1nMemory key * hap = halfSperm cell (1n) and egg cell (
1n
) create a diploid cell (
2n)Slide7
Section 8.1
Notice high number of chromosomes in fern compared to humans!Slide8
Section 8.1
Homework
Review questions on p. 153 #1-5Slide9
Section 8.1 Review Answers
Name the proteins that DNA wraps around to form a chromosome in eukaryotic cells.
Histones.How do the structure and location of a prokaryotic chromosome differ from that of a eukaryotic chromosome?A prokaryotic chromosome consists of a circular DNA molecule. Eukaryotic chromosomes are rod-shaped, associated with histone and nonhistone proteins, and found within the cell’s nucleus.Does chromosome number indicate whether an organism is a plant or animal? Explain.No. For example, chimpanzees have the same number of chromosomes as potatoes or plums.Slide10
Section 8.1 Review Answers
4. Contrast sex chromosomes with autosomes.
Sex chromosomes determine the gender of an organism. Autosomes are all of the other chromosomes in an organism.5. Using Table 8-1, list the haploid and diploid number of chromosomes for each organism.Slide11
Section 8.1 Review Answers
Organism
Diploid # ChromosomesHaploid # 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
26Slide12
Section 8.2
Cell Cycle
Repeating set of events in the life of a cellInterphaseTime between cell divisionsThree phasesG1 – Cell growthS – DNA is copiedG2 – Growth and prep for cell divisionCell divisionTwo phasesMitosis – Nucleus of the cell dividesCytokinesis – Division of the cell’s cytoplasmSlide13
Section 8.2
Cell Division
ProkaryotesRemember: Has cell wall, no nuclei, no membrane-bound organellesBinary fissionDivision of prokaryotic cell into two offspring cellsSlide14
Section 8.2
Cell Division (cont’d)
EukaryotesMitosisDivision of the nucleusFour stages (Prophase, Metaphase, Anaphase, Telophase)CytokinesisIn animal cells, pinching of cell membrane occursCleavage furrowIn plants, cell plate formation Slide15
Section 8.2
Control of Cell Division
Checkpoints = traffic signalThree main checkpointsG1 checkpointG2 checkpointMitosis checkpointSlide16
Section 8.2 (cont’d)
Mitosis
ProphaseTight coiling of DNA into chromosomesNucleolus and nuclear membrane break downCentrosomes appear and move to opposite ends of the cellKinetochore fibers extend from kinetochore from each chromatid to centrosomeMetaphase = MiddleKinetochore fibers move chromosomes to center of cell
All chromosomes line up in a single file lineSlide17
Section 8.2
Anaphase
Chromosomes separate at the centromere and chromatids move to opposite polesChromatids are now considered individual chromosomesTelophaseSpindle fibers disassembleChromosomes return to less tightly coiled chromatin stateNuclear envelope forms around each set of chromosomesNucleolus forms in each of the newly forming cellsAnimationSlide18
Mitosis vs Meiosis
Where do they occur?
Mitosis – in the body cells (Somatic Cells)Meiosis – in the germ cells (Sex Cells)Why does it occur?MitosisAsexual reproductionGrowth and developmentTo replace old cellsMeiosisFormation of gametes (egg and sperm cells) that will be used in sexual reproductionSlide19
Mitosis vs Meiosis
End result?
464646MITOSIS4623
23
23
23
23
23
MEIOSISSlide20
Meiosis
Also known as reduction division
Occurs in germ cells found in the ovaries and testesProduces sex cells which are haploidOccurs in two phasesMeiosis IReduces the number of chromosomes from diploid to haploidMeiosis IIProduces four haploid daughter cellsSlide21
Meiosis ISlide22
Meiosis IISlide23
Section 8.3
Results of mitosis vs. meiosisSlide24
Section 8.3
Development of Gametes
SpermatogenesisOogenesisPolar bodiesSexual reproductionSlide25
Why is meiosis important?
Increases genetic diversity in a population of species.
This helps to prevent organisms from mass extinction in the event of a plague or other disaster.Allows animals to adapt to a changing environment (natural selection)