Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Cytokinesis (after mitosis)Loss of Cell Cycle Controls in Cancer CellsSlide 11Slide 12Sets of Chromosomes in Human CellsSlide 14Slide 15Slide 16Meiosis reduces the number of chromosome sets from diploid to haploidSlide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Sexual reproduction1. Independent Assortment of ChromosomesSlide 282. Crossing OverSlide 303. Random Fertilization•The continuity of life is based on the reproduction of cells, or cell division•In unicellular organisms, division of one cell reproduces the entire organism•All the DNA in a cell constitutes the cell’s genome•Cell division is an integral part of the cell cycle, the life of a cell from formation to its own division•DNA molecules in a cell are packaged into chromosomes•Every eukaryotic species has a characteristic number of chromosomes in each cell nucleusCell division•Mitosis is the process of cell division that produces daughter cells with identical genetic information, this happens in the entire body except testis and ovary.•Meiosis is the process of cell division that produces gametes(sperm or egg) in reproductive organs, testis and ovary of male and female respectively.•Meiosis yields nonidentical daughter cells that have only one set of chromosomes, half as many as the parent cell1. Mitotic (M) phase (cell division phase)a. Mitosis (division of the nucleus)b. Cytokinesis(division of the cytoplasm)2. Interphase (cell growth and copying of chromosomes in preparation for cell division)•It’s about 90% of the cell cycle can be divided into subphases:–G1 phase (“first gap”)–S phase (“synthesis”)–G2 phase (“second gap”)In Mitosis- The Eukaryotic cell cycle consists of 2 phasesFig. 12-5S(DNA synthesis)MITOTIC(M) PHASEMitosisCytokinesisG1G2•Mitosis is conventionally divided into five phases:1. Prophase2. Prometaphase3. Metaphase4. Anaphase5. Telophase•Cytokinesis is well underway by late telophaseEukaryotic cell divisionFig. 12-6G2 of InterphaseCentrosomes(with centriolepairs)Chromatin(duplicated)NucleolusNuclearenvelopePlasmamembraneEarly mitoticspindleAsterCentromereChromosome, consisting of two sister chromatidsProphasePrometaphaseFragmentsof nuclearenvelopeNonkinetochoremicrotubulesKinetochoreKinetochoremicrotubuleMetaphaseMetaphaseplateSpindleCentrosome atone spindle poleAnaphaseDaughterchromosomesTelophase and CytokinesisCleavagefurrowNucleolusformingNuclearenvelopeforming•The mitotic spindle is an apparatus of microtubules that controls chromosome movement during mitosis by attaching itself to kinetochores.1. During prophase, assembly of spindle microtubules begins in the centrosome, the microtubule organizing center•The centrosome replicates, forming two centrosomes that migrate to opposite ends of the cell, as spindle microtubules grow out from them2. During prometaphase, some spindle microtubules attach to the kinetochores of chromosomes and begin to move the chromosomes3. At metaphase, the chromosomes are all lined up at the metaphase plate, the midway point between the spindle’s two poles.(metaphase is the longest phase)4. In anaphase, sister chromatids separate and move along the kinetochore microtubules toward opposite ends of the cell (anaphase is the shortest phase)•The microtubules shorten by depolymerizing at their kinetochore ends•Nonkinetochore microtubules from opposite poles overlap and push against each other, elongating the cell5. In telophase, genetically identical daughter nuclei form at opposite ends of the cellFig. 12-9Cleavage furrow100 µmContractile ring ofmicrofilamentsDaughter cells(a) Cleavage of an animal cell (SEM) (b) Cell plate formation in a plant cell (TEM)Vesiclesformingcell plateWall ofparent cellCell plateDaughter cellsNew cell wall1 µm•In animal cells, cytokinesis occurs by a process known as cleavage, forming a cleavage furrow. In plant cells, a cell plate forms during cytokinesisCytokinesis (after mitosis)Loss of Cell Cycle Controls in Cancer Cells•Cancer cells exhibit neither density-dependent inhibition nor anchorage dependence•Cancer cells do not respond normally to the body’s control mechanisms•Cancer cells may not need growth factors to grow and divide:–They may make their own growth factor–They may convey a growth factor’s signal without the presence of the growth factor–They may have an abnormal cell cycle control systemLoss of Cell Cycle Controls in Cancer Cells•A normal cell is converted to a cancerous cell by a process called transformation•Cancer cells form tumors, masses of abnormal cells within otherwise normal tissue•If abnormal cells remain at the original site, the lump is called a benign tumor•Malignant tumors invade surrounding tissues and can metastasize, exporting cancer cells to other parts of the body, where they may form secondary tumorsFig. 12-20TumorA tumor growsfrom a singlecancer cell.GlandulartissueLymphvesselBloodvesselMetastatictumorCancercellCancer cellsinvade neigh-boring tissue.Cancer cells spreadto other parts ofthe body.Cancer cells maysurvive andestablish a newtumor in anotherpart of the body.1234Sets of Chromosomes in Human Cells•A karyotype is an ordered display of the pairs of chromosomes from a cell •The two chromosomes in each pair are called homologous chromosomes•Each pair of homologous chromosomes includes one chromosome from each parent•Chromosomes in a homologous pair are the same length and carry genes controlling the same inherited characters•APPLICATION•TECHNIQUE•Pair of homologous•replicated chromosomes•5 µm•Centromere•Sister•chromatids•Metaphase•chromosomeThe sex chromosomes are called X and YThe 22 pairs of chromosomes that do not determine sex are called autosomesHuman males have one X and one Y chromosomeHuman females have a homologous pair of X chromosomes (XX)•Fertilization is the union of gametes (the sperm and the egg)•The fertilized egg is called a zygote and has one set of chromosomes from each parent •The zygote produces somatic cells by mitosis and develops into an adult•At sexual maturity, the ovaries and testes produce haploid gametes•Gametes are the only types of human cells produced by meiosis, rather than mitosis•Meiosis results in one set of chromosomes in each gamete•Behavior of Chromosome Sets in the Human Life Cycle•Fig. 13-5•Key•Haploid (n)•Diploid (2n)•Haploid gametes