Chapter 8

Chapter 8Cell Reproduction

http://biofinity.org/images/Cell%20Division%20Micrograph.jpgSection 1 Vocabulary PretestChromosomeHistoneChromatidCentromereChromatinSex ChromosomeAutosomeHomologous ChromosomeKaryotypeDiploidHaploidCells with one set of chromosomesCells with two sets of chromosomesRod-shaped structures made of DNA and proteinsProteins found in DNAX and Y chromosomesA chromosome other than a sex chromosomeAll chromosomes visible in a cellMatching chromosomesCopied half of a chromosomeHolds chromatids togetherDNA during interphase

Answer KeyChromosomeCHistoneDChromatidICentromereJChromatinKSex ChromosomeEAutosomeFHomologous ChromosomeHKaryotypeGDiploidBHaploidA

Why Cells DivideGrowth and repairCreation of gametes (Sex Cells)Method of reproduction in unicellular organisms

http://stealthisknowledge.com/Pictures/images-mesoblast_cell_division_still.jpgChromatinWhile cells are growing, their DNA appears as long, stringy chromatin material.When cells are ready to divide, the chromatin condenses to form chromosomes.

http://kmarsh2.umwblogs.org/files/2008/10/mitosis_cartoon_1.jpgChromosomesChromosomes DNA wrapped around proteins to form an X-shaped structureHistones proteins that DNA wraps aroundSections of chromosomes are called geneshttp://www.youtube.com/watch?v=9kQpYdCnU14 (go to real player video folder on desktop: How DNA is packaged)

Histoneshttp://activity.ntsec.gov.tw/lifeworld/english/content/images/en_gene_c5.jpgChromosome StructureEach chromosome is made of two identical halves called sister chromatids held together at a point called a centromere.The sister chromatids are the result of DNA copying itself. They are called double stranded and will need to separate before the cell divides.

http://www.biologycorner.com/resources/chromosome-labeled.gifChromosome NumbersHumans have 46 chromosomes in the nucleus of every cell Two are the sex chromosomes (X and Y)XX = femaleXY = maleThe other 44 are called autosomesThey occur in matching pairsCalled homologous chromosome pairsOne chromosome in each pair comes from mom and the other comes from dad

KaryotypesA karyotype is a photograph of the matching pairs of chromosomeshttp://www.youtube.com/watch?v=V8sNC9Cdv0E&feature=related (go to real player video folder on desktop: What is a Chromosome?)

http://www.mathemagic.org/MOBM/images/karyotype.jpgDiploid vs HaploidDiploid cells contain the full set of chromosomes (all 46)All body cells are diploidHaploid cells contain half the number of chromosomes (23)One from each homologous pairSperm and egg cells are haploidSection 2 Vocabulary PretestBinary fissionMitosisAsexual reproductionMeiosisGametesInterphaseCytokinesisProphaseSpindle fiberMetaphaseAnaphaseTelophaseCell plateDivision of cells cytoplasmDivision of cells nucleusReproductive cellsDivision of a prokaryotic cellPull chromatids apartChromosomes line up in middle of the cellChromatids separateTwo new nuclei formProduction of offspring from one parentTime between cell divisionsResults in the formation of gametesFirst phase of mitosisForms between two new plant cells

Answer KeyBinary fissionDMitosisBAsexual reproductionIMeiosisKGametesCInterphaseJCytokinesisAProphaseLSpindle fiberEMetaphaseFAnaphaseGTelophaseHCell plateM

Cell Divisionhttp://www.youtube.com/watch?v=Q6ucKWIIFmg (go to real player video folder on desktop: Cell Division and the Cell Cycle)How many new cells do you make every day?About 2 trillion (25 million cells per second)Cells reproduce asexually (one parent)One cell becomes twoThe process is different in prokaryotes and eukaryotesCell Division in ProkaryotesProkaryotes reproduce by binary fissionDNA is circular (no chromosomes)DNA copies itselfCell divides---Simple

Cell Division in EukaryotesEukaryotes use two types of cell divisionMitosis produces body cellsMeiosis produces gamete cellsBoth mitosis and meiosis happen in stages

http://ghr.nlm.nih.gov/handbook/illustrations/mitosismeiosis.jpgThe Cell CycleMitosis is part of the Cell CycleThree stages in the Cell Cycle:Interphase period of growth, development and DNA replicationMitosis division of the nucleusCytokinesis division of the cytoplasmhttp://www.youtube.com/watch?v=lf9rcqifx34&feature=related (go to real player video folder on desktop: Cell cycle )

http://faculty.capebretonu.ca/cglogowski/BIOL%20101%20IMAGES/CellCycle_L.jpgInterphaseCells spend most of their time in interphaseThree phasesG1first growth phase (Cells grow to full size)SDNA synthesis (copied)G2second growth phase (prepares to divide)

http://imcurious.wikispaces.com/file/view/cell_cycle.jpg/114427989/cell_cycle.jpgSome cells exit the cycle after the G1 phase and enter the G0 phase. These cells no longer divide.Muscle cellsNerve cells

MitosisMitosis (division of nucleus) is divided into four stages:ProphaseDNA condenses into chromosomesNuclear membrane disappearsCentrioles and spindle fibers appearMetaphaseChromosomes line up in the middle of the cellAnaphaseSister chromatids separate and move toward polesTelophaseChromosomes uncoil back into chromatinNuclear membrane forms around each set of chromosomes

Interphase Prophase Metaphase Anaphase TelophaseStages of Mitosishttp://www.clt.astate.edu/mhuss/mitosis1.jpgCytokinesisThe final stage of the cell cycle is cytokinesis (dividing the cytoplasm)In animal cells, cytokinesis begins with a pinching in of the membrane forming a cleavage furrow.In plant cells, cytokinesis begins with the formation of a cell plate.End result is two identical diploid daughter cells

http://www.uic.edu/classes/bios/bios100/lectf03am/cleavage.jpg

http://www.vcbio.science.ru.nl/images/cellcycle/mito_solanum_cellplate.jpgMeiosisMeiosis produces gamete cells (sperm and egg cells)Gamete cells are haploid (half the number of chromosomes)Full number of chromosomes is restored during fertilization. A cell passes through interphase and copies its DNA.The cell then divides twice resulting in 4 haploid gamete cells.

Meiosis is also divided into stages:Prophase IChromosomes form and find their homologous matchThis is called synapsis (pairing of homologous chromosomes)Each pair of homologous chromosomes is called a tetrad.Crossing over can occur in each tetrad resulting in a genetic recombination of genes.

http://www.biologycorner.com/resources/crossingover.jpgMetaphase IMatching pairs of chromosomes (tetrads) line up in the middle of the cell and attach to spindle fibers. Anaphase IHomologous chromosomes separate and move to the poles (independent assortment)Telophase I and Cytokinesis INucleus and Cell both divide for the first time. This reduces the number of chromosomes to one half. This is called a reduction division.However, the chromosomes are still double stranded.

Prophase IISpindle fibers reappear Metaphase IIChromosomes line up in the middle of the cell and attach to spindle fibersAnaphase IIChromatids split and move to polesTelophase II and Cytokinesis IINucleus and cell divide for the second timeThis is essentially a mitotic division.4 haploid gamete cells are produced. They have half the number of single stranded chromosomes.

http://www.phschool.com/science/biology_place/labbench/lab3/images/stages2.gif(go to real player video folder on desktop: Meiosis Sq. Dance)

http://www.biologycorner.com/resources/oogenesis.jpgMeiosis occurs in the testes and the ovariesSpermatogenesis production of 4 mature sperm cells.Oogenesis production of 1 mature egg cell and 3 smaller polar bodies that degenerate.FertilizationFertilization union of sperm and egg cell. Sexual reproduction, involving the production of sperm and egg cells by meiosis followed by fertilization, ensures genetic variation in all offspring.

http://biology.ucsd.edu/classes/bimm110.SP07/images/fertilization2.jpg