2Review Organelles Centrioles Mitotic Spindle fibers Nuclear envelope Made 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 nucleus
3Section 8.1 Chromosomes Chromosome Structure Chromatid Centromere Rod-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 centerCentromereCenter where chromatids areheld togetherChromatinLess tightly coiled DNA-protein complexTin = thin *Think spaghettiForm taken during transcriptionChromatid is
4Section 8.1 Sex Chromosomes Autosomes Determine gender of the organism May 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)
5Section 8.1 Homologous Chromosomes Karyotype 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?
6Section 8.1 Diploid Haploid 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 cellsHaploidCells 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)
7Section 8.1Notice high number of chromosomes in fern compared to humans!
8Section 8.1 Activity Homework Create a karyotype! Arrange in pairs according to length, centromere position, and banding patternQuestionsHow many autosomes are there? How many sex chromosomes?Is the organism a male or female?Why are karyotypes important tools for geneticists?HomeworkReview questions on p. 153 #1-5
9Section 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.
10Section 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.
12Section 8.2 Cell Cycle Repeating set of events in the life of a cell InterphaseTime 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 cytoplasm
13Section 8.2 Cell Division Prokaryotes Remember: Has cell wall, no nuclei, no membrane-bound organellesBinary fissionDivision of prokaryotic cell into two offspring cells
14Section 8.2 Cell Division (cont’d) Eukaryotes Mitosis Cytokinesis Division of the nucleusFour stages (Prophase, Metaphase, Anaphase, Telophase)CytokinesisIn animal cells, pinching of cellmembrane occursCleavage furrowIn plants, cell plate formation
15Section 8.2 Control of Cell Division Checkpoints = traffic signal Three main checkpointsG1 checkpointG2 checkpointMitosis checkpoint
16Section 8.2 Activity Homework Venn diagram: Cell division in Prokaryotes vs EukaryotesKaryotype Part 2HomeworkCreate the cell cycle
17Section 8.2 (cont’d) Mitosis Prophase Metaphase = Middle Tight 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 cellAll chromosomes line up in a single file line
18Section 8.2 Anaphase Telophase Animation 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 cellsAnimation
19Mitosis vs Meiosis Where do they occur? Why does it occur? Mitosis – in the body cellsMeiosis – in the germ cellsWhy does it occur?MitosisAsexual reproductionGrowth and developmentTo replace old cellsMeiosisFormation of gametes (egg and sperm cells) that will be used in sexual reproduction
20Mitosis vs Meiosis End result? MEIOSIS MITOSIS 46 46 23 23 46 46 23 23
21Meiosis 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 cells
23Meiosis I Prophase I DNA coils tightly into chromosomes Spindle fibers appearNucleolus and nuclear envelope disassembleSynapsis =Pairing of homologous chromosomesTetrad =Pair of homologous chromosomes twisted around each otherCrossing over may occurGenetic recombination
24Meiosis I Metaphase I Anaphase I Telophase I Spindle fibers attach to centromere of tetradsTetrads line up along midlineAnaphase IHomologous chromosome pairs are separated and move to opposite polesIndependent assortment occursTelophase IChromosomes reach opposite ends of cellSpindle Fibers disappearCytokinesis begins
26Meiosis II Prophase II Metaphase II Anaphase II Telophase II Spindle fibers form and attach to the centromeres of the double stranded chromosomesMetaphase IIChromosomes are moved to the midline of the dividing cellAnaphase IIChromatids separate and move toward opposite polesTelophase IINuclear membrane forms in each of the four new cellsCytokinesis II occurs resulting in four new cells, each with half the original cell’s number of chromosomes