12/5/19 Bellringer Bellringer 12/4/19 Chromosomes

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12/5/19Bellringer12/3/19 - Reproduction 2. Identify the type of reproductionthatresults in geneticallyidentical offspring. results in geneticallydifferent offspring: has 1 parent has 2 parents Bellringer 12/4/19Chromosomes1. Each chromosome joins two identical copiescalled , that arejoined at the .Draw a picture to accompany this statement!2. How many chromosomes are in the karyotypebelow? See pic below. 3. Why is it important for cells toreproduce? List at least tworeasons.Bellringer 12/5/19Cell CycleA cell spends most of its timein which stage of the cellcycle?2. When in the cell cycle is DNAsynthesized (copied)?3. What cell structure pullschromosomes through thestages of cell division?Bellringer 12/6/19Mitosis1.Identify the stage of mitosiso A.The chromosomes line up in the middleThe sister chromatids pull aparto C. The chromosomes become visibleo D. Two daughter nuclei are presento B.BellringerBellringer 12/10 PLEASE GET YOUR SEM.1EXAM REVIEW GUIDE OUT1. How are sister chromatids andhomologous chromosomesdifferent?2. Draw a picture to show thedifference.3. Explain why not all humanshave 23 homologous pairs ofchromosomes. (hint: thinkabout the sex chromosomes).What is the human diploid and haploid number ofchromosomes? Give a type of cell where thatnumber of chromosomes would be found.Fill in the blanks using the following words: Interphase,S Phase, Chromosomes, Chromatin, sisterchromatids, Chromosomes,The genetic material called , containsDNA and other proteins. It condenses in Prophaseto form , which are now visible. Eachis made up of twothat have identicalinformation found on them. The copy of geneticmaterial was made during the of.1

12/5/19BellringerCompare and Contrast Meiosis andMitosis in a Venn Diagram.Bellringer 24. If a diploid cell has 40 chromosomes, howmany chromosomes will be present in the cells atthe end of A. B.Mitosis?Meiosis? 25. What three ways increase genetic variation insex cells? If an organism has diploid cells with 20chromosomes, how many genetic combinationsare possible in the sex cells?What do you know?Unit 2 – Heredity: Inheritance andVariation of Traits The division of cells into more cells enables livingthings to repair damage, to grow, and to produceoffspring.Words that come to mind when youthink of cell’s dividing .Repair and Growth Important roles ofcell reproduction thereplacement oflost or damaged cells(repair) growth—simplyincreasing in sizeCell reproduction enables yourbody to produce new skincells that replace dead cells atyour skin's surface.2

12/5/19Reproduction While the production of new cells can result ingrowth and repair within organisms, cell divisionalso has an essential role in the reproduction ofentire organisms 2methods of Reproduction Asexual reproduction Sexual reproductionAsexual Reproductionvideo clipAsexual ReproductionAsexual reproduction : organisms reproduce by simple celldivision, in which a single cell or group of cells duplicatesits genetic material and then splits into two new geneticallyidentical cells. offspring offspringinherit all their genetic material from just one parent.are genetically identical to one another and to theirparent.Asexual Reproduction Examples: BinaryFission – asingle cell divides intotwo equal parts. Examples: Paramecium E.coliSexual Reproduction Sexual reproduction : two parents are involved inthe production of offspring; genetic material fromeach parent combines, producing offspring thatdiffer genetically from both parents.bacteria Multicellularorganisms atcertain times intheir life cycle. Examples: StrawberriesReproduction and Growth Whether reproduction is sexual or asexual, allmulticellular organisms depend on cell division forgrowth. Examples:involves the union of sex cells, such asan egg and a sperm.3

12/5/19Let’s make a foldable! Follow my close instructions on how to make TheCell Cycle Foldable.The Cell Cycle Multiplies Cells Page Headings 1.The Cell Cycleyour name at the bottom 2. Interphase 3. The Mitotic Phase – Prophase 4. The Mitotic Phase – Metaphase 5. The Mitotic Phase – Anaphase 6. The Mitotic Phase – Telophase 7. Cytokinesis 8. Important Vocabulary PutChromatinThink about it Genetic material is located inthe cell nucleus, and exists asa mass of very long fibers thatare too thin to be seen under alight microscope- At this moment, millions of cells in your body aredividing, each forming two new cells. However, the vast majority of your cells (about200 trillion) aren't dividing but are going aboutother cell activities— Thisis chromatin, long fibersof DNA and protein moleculescombined. buildingproteins breaking down food consuming energy and so on How does cell division fit into the life of a cell?Chromosomes Asa cell prepares to divide, its chromatin fiberscondense, becoming visible as the compact structurescalled chromosomes. Each chromosome may contain many hundreds of genesChromosomes Thenumber of chromosomes in a eukaryotic celldepends on the species. For example, human body cells generally each have 46chromosomes, gorilla 48, mouse 40, fruit fly 12.4

12/5/19The Cell CycleChromosomes and Cell Division Eukaryotic cells that divide undergo an orderly Before cell division begins, a cell duplicates all ofsequence of events known as the cell cycle.its chromosomes. Each chromosome now consists of two identicaljoined copies called sister chromatids. The region where the two chromatids are joinedtightly together is called the centromere. The cell cycle extends from the "birth" of a cell tothe time the cell reproduces 2 Main phases: Interphase MitoticInterphasephaseInterphase 1. G1 Phase: cell is growing 1. Interphase is the stage during which a cellcarries out its metabolic processes and performsits functions. Cellis just living its life 90 percent of cell life spent in this phase. 3 phases: 1. G1 2. S 3. G2 -Mitotic Phase Gstands for gap 2. S phase: key event,duplication of the DNA inthe cell's chromosomes.S stands for DNAsynthesis 3. G2 phase: eachduplicated chromosomeremains loosely packed aschromatin fibers and thecell grows. The cell is nowready to begin mitosis.Mitotic Phase Mitosis nucleusand the duplicated chromosomes divide and areevenly distributed, forming two "daughter" nuclei. Mitotic phase: (Mphase) the stageof the cell cyclewhen the cell isactuallydividing Cytokinesis process usuallyby which the cytoplasm is divided in two.begins before mitosis is completed. includestwoprocesses Mitosis CytokinesisMITOSISCYTOKINESIS5

12/5/19Trivia: How often do cells divide?Cell Division and The Cell Cycle How often a celldivides depends on thetype of cell. Somecells divide oncea day. Some divide moreoften; others, lessoften. Some highlyspecialized cells, suchas mature musclecells, do not divide atall.Mito/cSpindleThe Mitosis DanceCells divide during the MitoticPhase Mitotic SpindleCentrioles Football-shaped framework ofmicrotubules that guidechromosome movement duringmitosis CentrosomesCentrosomes spindle microtubules grow from2 centrosomes, regions ofcytoplasmic material that, inanimal cells, contain structurescalled centrioles. Centrioles The role of centrioles in celldivision is a mystery. Destroyingthem has no effect6

12/5/19The Mitosis Dance Mitosis is a CONTINUAL process. the mitotic phase has been divided into 4 main stagesInterphase! The cell is busy making newto aid study:molecules and organelles.! Cell has duplicated its DNA.! Can't see chromosomes yet-still loosely packedchromatin fibers.! The presence of thenucleolus indicates that thecell is still 4.Telophase1. Prophase2. Metaphaseo “MIDDLE”o 1st Stage of Mitosiso second stage, shorto chromosomesall gatheracross the middle of thecello mitotic spindle fullyformedo All chromosomes areattached to the spindlewith their centromereslined up about halfwaybetween the two ends of thespindle.o chromosomes visibleo Each chromosome can be clearly seeno now to (consist of a pair of sistero chromatids joined at the centromere.)o nucleolus disappears-cell stops makingribosomes.o nuclear envelope breaks down.o mitotic spindle forms.o chromatids attach to spindle.o spindle starts tugging the chromosomestoward the center of the cell for the nextstep in the dance.3. Anaphaseoo4. Telophase“APART”3rd Stageoo sister chromatids separateofrom their partners.o Each chromatid is now adaughter chromosome, thatwill move along the spindletoward the ends.o Some microtubules shorten,bringing chromosomescloser to the poles.o Some spindle microtubulesnot attached to centromeresthey do the opposite— growlonger, pushing the polesfarther apart.oooooFinal PhaseReverse of prophasespindle disappearstwo nuclear envelopesreform (one around each setof daughter chromosomes)the chromosomes uncoiland lengthennucleoli reappear.Mitosis, the division of onenucleus into two geneticallyidentical daughter nuclei, isnow finished.7

12/5/19CytokinesisCytokinesis in Animalsoo Cytokinesis completes the cell division processo Itdivides the cytoplasm into two daughter cells,each with a nucleus.o Occurs along with telophase.Animal cellso first sign of cytokinesis is the appearance of an indentation aroundthe middle of the cello Pinching apart of cell.o two new nuclei are forming at the ends of the cell, cytokinesisresults in two new cells.Cytokinesis in Plantso Cytokinesis in a plant cell occurs differentlyo A disk containing cell wall material called acell plate forms inside the cell and grows outward.o new piece of cell wall divides the cell in two.o result is two daughter cells, each bounded by itsown continuous membrane and its own cell wall.Cancer Cells Grow and Divide Outof Control8

12/5/19How do cancer cells differ fromnormal cells?Tumors and Cancero The timing of cell division iscritical to normal growth anddevelopment.o "controlsystem" made ofproteins in cell directs sequenceof events in cell cycle.o control system malfunction cells reproduce at wrong time orin wrong place.o Out-of-control cell reproductioncan produce a mass of cellscalled a tumor.Benign Tumoro Benign tumor: an abnormal mass of essentiallynormal cellso Dependingon location in the body, benign tumorscan cause health problemso usually they can be completely removed by surgeryo cells of benign tumors always remain at theiroriginal site in the body.Malignant Tumoro Malignant Tumor: more problematic than benign,masses of cells that result from the reproduction ofcancer cells9

12/5/19Cancero Cancer is a disease caused bythe severe disruption of themechanisms that normallycontrol the cell cycle.o disruptionleads to uncontrolledcell divisiono if unchecked can result indeath.o most dangerous characteristicof cancer cells is their ability tospread.CancerA malignant tumor displaces normal tissue as it grows.o If a malignant tumor is not killed or removed, it canspread into surrounding tissues.o More alarming still, cells may split off from the tumor andtravel to other parts of the body, where they can formnew tumors.o The spread of cancer cells beyond their original site iscalled metastasisoCancero Many different biochemicalchanges can affect the cell cycleand result in cancer.o Thus, there is no single "cure," butrather multiple approaches tocontrolling or halting the progressof the disease.Cancer Treatmento When possible, malignant tumorsSurgical Removal of Malignant Tumorare removed by surgery.o difficult to successfully remove alltraces of cancer cells withsurgery.o Treat cancer at cellular level!radiation therapy orchemotherapy.o Bothattempt to stop cancer cellsfrom dividing.10

12/5/19Cancer Treatmento Radiation Therapyo theparts of the body with cancerous tumors are exposedto high-energy radiation- which disrupts cell division.o Because cancer cells divide more often than mostnormal cells, they are more likely to be dividing at anygiven time.o So radiation can often destroy cancer cells with minimaldamage to normal cells (who spend 90% of time ininterphase-not dividing).Cancer Treatmento Chemotherapyo involvestreating the patient with drugs that disrupt celldivision.o These drugs work in a variety of ways.o Some, called antimitotic drugs, prevent cell division byinterfering with the mitotic spindle.o One antimitotic drug prevents the spindle from forming in thefirst place.o Another drug "freezes" the spindle after it forms, keeping it fromfunctioning.Cancer Treatmento Side Effectso Bothradiation and chemotherapy can causeundesirable side effects in normal body cells thatdivide fairly often.o Radiation, for example, can damage cells of theovaries or testes, causing sterility.o Intestinal cells or hair follicle cells can be affectedby chemotherapy, leading to nausea or hair loss.The Anatomy of CancerGenomic Testing of Cancer11

12/5/19Skin Cancer PreventionThe cancer gene we all have Let’s Review Meiosis Functions in SexualReproductionHomologous Chromosomeso Sexual reproduction depends in part onMEIOSIS.o Meiosis- type of cell division that produces fourcells, each with half the number of chromosomes asthe parent cell.o Forms sex cells sperm and eggo Sexual reproduction involves thefusion of male and female gametes.o The resulting cell is called a zygote.Homologous Chromosomeso ALL cells of a single organism have same number andtypes of chromosomes.o Cells from different male or female individuals of a singlespecies have the same number and types ofchromosomes.AllnormalHumanfemaleso Occurs in the sex organs—the testes in males and theovaries in females.12

12/5/19KaryotypeHomologous Chromosomeso Homologouschromosomes : the two chromosomes ofeach matching pair.oAdisplay of thechromosomes ofan individual iscalled a karyotype.o Resemble each other in size and shape and geneso Inheritone chromosome of each pair from your motherand the other from your father.o Humans have 46chromosomes intheir karyotype.MomGenes on Homologous Chromosomeso Each homologous chromosome in a pair carries the samesequence of genes controlling the same inheritedcharacteristics (height, eye color).o However, the two genes may be different versions.ooEx. Gene eye color, versions of eye color blue, brown, green Ex. Gene height, versions short, tallEyeColorEyeColorDadHomologous Chromosome vs. Sister Chromatido Homologouschromosomes are different from sister chromatidso Homologous Chromosomeso Have the same sequence of genes on each chromosome in the pair butmay carry different versions of the same geneo Sister chromatidso are duplicated copies of a single chromosome that are attached to eachother and are identicalo both chromatids contain EXACTLY the same forms of each eightBloodTypeSex Chromosomeso Humans have 22-23 homologous pairs ofchromosomes.o #23 determine sex ! sex chromosomeso Females have 23 homologous chromosomeso Males have 22 homologous chromosomes13

12/5/19Sex Chromosomeso 2 forms of the sex chromosome: X & YDiploid and Haploid Cellso 2 sets of chromosomesomales have one X chromosome and one Y chromosome (XY at #23)o1ofemales have two X chromosomes (XX at #23)o Thiso Most genes carried on the X chromosome do not havecounterparts on the tiny Y, and the Y has genes that are not onthe XDiploid Cellsinherited from each parentis a key factor in the life cycles of all sexuallyreproducing organisms.Haploid Cellso Haploid : (half) cell with a single set of chromosomeso Foro Almost all human cells are diploido diploid: they contain two homologous sets of chromosomes.o The total number of chromosomes, 46 in humans, isreferred to as the diploid numbero (abbreviatedhumans, the haploid number (abbreviated n) is 23.o haploid cells are produced through the process of meiosiso Each gamete has a single set of chromosomes, one from eachhomologous pair.o Ex:gametes : sex cells , or egg and sperm cells2n, as in 2n 46).2323Haploid and Diploid cellso Fertilizationo thenucleus of a haploid sperm cell from the father fuseswith the nucleus of a haploid egg cell from the motherHaploid and Diploid cellso Zygote: fertilized egg, diploid cell.o has two homologous sets of chromosomes, one set from each parent.o develops into a sexually mature adult with trillions of cells produced bymitosis.o fertilizationrestores the diploid chromosome number, andthe zygote's 46 chromosomes are passed on to all the otherHaploidn 23diploid body cells.Diploid2n 46Diploid2n 46HomologousChromosomes!!!Diploid2n 4614

12/5/19Sexual ReproductionLife Cycle DiagramThe Importance of MeiosisoProducing haploid gametes by meiosis keeps thechromosome number from doubling in every generation.o If meiosis did not occur, cells involved in fertilization wouldproduce new organisms having twice the number ofchromosomes as those in the previous generation.o The alternation of meiosis and fertilization keeps the number ofchromosomes in a species the same from generation togeneration.46o#23Use the following words to match the # to what is taking place in the cell.AnaphaseZygoteFertilizationHaploid EggHaploid SpermTelophase/cytokinesis Diploid DAD cellDiploid MOM cell?46 92?Meiosis:The ProcessMeiosis Versus Mitosiso MEIOSIS is different from MITOSIS in 2 major ways.o 1st major differenceo Meiosis produces 4 new offspring cells, each withone set of chromosomes— 1/2 the # ofchromosomes as parent cello Mitosis produces 2 offspring cells, each with thesame number of chromosomes as the parent cell.o 2nd major differenceo Meiosis involves the swapping of genetic materialbetween homologous chromosomes- crossing overThe Two Meiotic Divisionso Meiosis consists of two distinctparts—o Meiosis Io homologous chromosomes with sisterchromatids, separate from oneanotherMeiosisIo Meiosis IIMeiosisIIo sister chromatids are separated muchas they are in mitosis.o However, the resulting cells arehaploid, NOT diploid.15

12/5/19Prophase Io Meiosis adds 2 new steps to themitosis routine.o 1)Tetrads:o Homologous chromosomes to sticktogether along their length.o Homologous chromosomes arepaired, and consist of fourchromatids, referred to as tetrads.o The tetrads attach to the spindle.o 2)Crossing Over:o Sister chromatids in the tetradsexchange some genetic material inthe process known as crossingover.Anaphase IMetaphase ITetrads move to the middle of the cell and lineup across the spindle.Homologous chromosomesseparate and migrate toopposite poles of the spindle.Sister chromatids migratetogether—each chromosome ismade up of two copies.Genes split in half. Thiscell started with 4chromosomes, there are only2chromosomes (each with 2copies) moving to each pole.Telophase I and CytokinesisoChromosomes with sisterchromatids arrive at the polesforming Haploid daughter esplit50:50o Each has only one set ofchromosomes, even though eachchromosome consists of two sisterchromatidsCytokinesis occurs withtelophase I, forming two haploiddaughter cells.o The chromosomes in eachdaughter cell are stillduplicated.o16

12/5/19Prophase II:Metaphase II:In each haploid daughter cell, a spindle forms,attaches to the centromeres, and moves theindividual chromosomes to the middle of the cell.The chromosomes line up in the middle of the cellwith spindle microtubules attached to each sisterchromatid.Anaphase II:The sister chromatids separate and move toopposite poles.Telophase II and Cytokinesis:o The chromatids, now considered individualchromosomes, arrive at the poles.o Cytokinesis splits the cells one more time.o The process of meiosis is completed, producing fourhaploid daughter cells as a final result.17

12/5/19Steps of Meiosis ISteps of Meiosis IIIn humans, n 23,so 2n 46.n 23 inhumans18

12/5/19Meiosisvs.Mitosis(All 46)(Line up in23 pairs.)(23 in each)(All 46)Assortments of Chromosomeso Assortment of chromosomes is completely randomMeiosis increases genetic variationamong offspring.o Metaphase I:o chromosomes in each homologous pair (tetrads) line up andseparate at random (by chance)o Resulting cells:o the assortment of chromosomes that end up in the resulting cellsoccurs loidchromosomenumberoffour(2n 4)Assortment and ProbabilityGenetic Variationo With haploid number, you can calculate thenumber of possible combinations in the gametes.o 2n # of possible combinationsonis the haploid number.For the organism in theexample, n 2, so thenumber of chromosomecombinations is 22, or 4.For a human, n 23, sothere are 223, or about 8million, possiblechromosomecombinations!3 Chromosomal factors that contribute to geneticvariationo 1.Crossing overIndependent Assortment - The number ofdifferent chromosome combinations in gameteso 3. Fertilizationo 2.19

12/5/19Crossing Overo 1. Crossing over—the exchangeMethods of genetic recombination:1. Crossing overof genetic material betweenhomologous chromosomeso occursduring prophase I ofmeiosiso Crossing over processo homologouschromosomesclosely paired along their lengths.o precise gene-by-gene alignmentbetween adjacent chromatids ofthe two chromosomes.o Segments of the two chromatidscan be exchanged at one ormore sites.Homologouschromosomesalign.Methods of genetic recombination:2. Independent assortment ofchromosomes.12320

12/5/19Methods of genetic recombination:3. FertilizationMitosis vs. Meiosis ology.html .htmlWhen the gametes fuse at fertilization, the chromosomesdonated by each parent are combined. In humans, thismeans that (223)2, or 70,368,744,000,000 chromosomallydifferent zygotes are possible for every couple, if nocrossing over occurs.o If crossing over occurs only once, then (423)2, or4,951,760,200,000,000,000,000,000,000 geneticallydifferent zygotes are possible for every couple.o21

Chromosomes As a cell prepares to divide, its chromatin fibers condense, becoming visible as the compact structures called chromosomes. Each chromosome may contain many hundreds of genes Chromosomes The number of chromosomes in a eukaryotic cell depends on the species.

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