Mitosis & Meiosis - Weebly
MITOSIS & MEIOSISBio Review
MITOSISPart 1
THE CELL CYCLE AND MITOSISDue to the loss and death of cells must replace them.How many cells in your body? 50-100 million trillion Every minute your body produces about 300 million new cellsThree stages in the cell cycle:1. Interphase: cell carries out normal functions.2. Mitosis: nucleus contents duplicated and divided intotwo equal parts.3. Cytokinesis: separation of two nuclei and cell contentsinto two daughter cells.
PARTS OF THE CELL CYCLE
INTERPHASEInterphase - the longest cell cycle stage (lasts 15 hrs. – months). cell performs normal functions and grows.In late interphase, DNA copies itself in the process ofreplication.Replication involves several steps:1. The DNA molecule unwinds with the help of an enzyme.2. New bases pair with the bases on the original DNA.3. Two new identical DNA molecules are produced. Now, double the amount of DNA in nucleus it divides (Mitosis)
DNA UNRAVELING (VIDEO)
LATE INTERPHASE CONT’D.Chromatin is in its loosely coiledform so that DNA can be copiedinto RNA for proteins to be made inpreparation for cell division.At the end of interphase, the cellcontinues to grow and makeproteins in preparation for mitosisand cytokinesis.
CHROMOSOMESAs the nucleus prepares to divide,replicated DNA in interphase joins to formsister chromatids, joined by a centromere.
MITOSIS OVERVIEW:Mitosis is the shortest stage of the cell cycle where thenuclear contents divide, and two daughter nuclei areformed.It occurs in 4 stages:1.2.3.4. ProphaseMetaphaseAnaphaseTelophaseHelpful saying to remember the order:“I picked many apples today.”
MITOSIS - PROPHASEChromosomes start to coil andbecome visible.Pairs of centrioles start toseparate.The nuclear membranedisappears.Spindle fibers start to formbetween the centriole pairs.Chromosomes move moreevenly throughout the nucleus.
MITOSIS - METAPHASECentriole pairs move toopposite ends of the cell.Spindle fibers are stillattached to the centriolepairs.Chromosomes line up alongthe midline of the cell andare attached to the spindlefibers.
MITOSIS - ANAPHASEThe pair of chromatids split atthe centromere and move toopposite ends of the spindle.Now there are twice the numberof chromosomes within the cellmembrane.Movement of the chromosomestowards the opposite ends ofthe cell membrane is aided bythe spindle fibers.
MITOSIS - TELOPHASENuclear membranes formaround the two new sets ofchromosomes.The spindle fiber disappears.Chromosomes start to uncoil(chromatin) and become lessvisible.Cell starts to make a groove(furrow) in the middle toeventually split into twoidentical cells.
CYTOKINESISThe division of material outsideof the nucleus. Occurs after telophase.Divides the organelles and othersubstances in the cytoplasm intoroughly two equal halves.Animal cells furrow while plantcells form a cell plate# chromosomes in daughter cell the # chromosomes in parentcell.Daughter cells are geneticallyidentical to parent.Video on Mitosis
MEIOSISPart 2
OBJECTIVESBy the end of the lesson you should be able to:Describe the process of meiosisCompare and contrast meiosis and mitosisExplain why meiosis is needed
MEIOSISSexual reproduction – 2 parents – genetic differencesThe process of Meiosis results in the production of special cells calledgametesGametes have half the number of chromosomes as body cells
MEIOSISCell division occurs twice in Meiosis Once at the end of Meiosis I and again at the end of Meiosis IIIn Meiosis I, matching chromosomes are called homologous chromosomesseparateIn Meiosis II, sister chromatids separate
MEIOSISThe process of meiosis shuffles genetic information and results invariation of the gametesGenetic diversity
MEIOSISAKA: Germ cell divisionPurpose: to producegametes (i.e. sex cells:sperm and egg)Products: 4 haploid cellseach genetically different this creates geneticvariability
TERMS:Haploid: half the total number of chromosomes found in gametes (inhumans 23)Diploid: total number of chromosomes found in body cells (in humans 46)
FERTILIZATION2 gametes come together; in humans an egg and sperm cometogetherEach has 23 chromosomes, thus together there is 46 in the zygote23 4623Gametes: why is thesperm smaller than theegg?Zygote: will grow (bymitosis) into a baby in 9 months
MEIOSIS: REDUCING CHROMOSOME NUMBER
NUMBER OF CHROMOSOMES SEQUENCE46Parent Cell924646232323All genetically different23DaughterCells
CHROMOSOME SEQUENCEMeiosis VideoMeiosis 2 Video
MEIOSIS – PROPHASE IChromosomes coil andbecome visible.Nuclear membranedisappears.Spindle fibers form.Homologouschromosomes movetowards each other andpair.
MEIOSIS – METAPHASE IPairs of homologouschromosomes move to themidline of the cell.These pairs are alignedon either side of themetaphase plate.
MEIOSIS – ANAPHASE IHomologous chromosomepairs are pulled awayfrom each other towardsopposite ends of the cell.Paired chromatidsremain attached.
MEIOSIS - TELOPHASE IPaired chromatids mayuncoil and become lessvisible.Nuclear membranes mayform around eachchromosome cluster.Spindle fibers disappear.Cytokinesis occurs.
MEIOSIS IIPhase II of meiosis is the mitotic division of haploid cells.Although there will be four new non-identical cells at the end ofmeiosis II, all other processes for this division are similar to mitosis.
MEIOSIS II – PROPHASE IIPaired chromatids coil.Spindle fibers form.Nuclear membranedisappears.
MEIOSIS II – METAPHASE IIPaired chromatids lineup in the middle of thecell.The chromatids areattached to spindlefibers.
MEIOSIS II – ANAPHASE IIEach pair of chromatidssplit at the centromere toform two independentchromosomes.Chromosomes move toopposite ends of the cell.
MEIOSIS II – TELOPHASE IIChromosomes uncoil andbecome less visible.Nuclear membranes fromaround four new nuclei.Spindle fibers disappear.Cytokinesis occurs.Meiosis Square Dance
MEIOSIS - CYTOKINESISSame process as in mitosis.Four non-identical cells areformed.These cells are calledhaploid cells (n).# chromosomes half the# of chromosomes ofparent cell.
MEIOSIS EVENTSMeiosis IMatching chromosome pairs(homologous chromosomes )move to opposite poles of the cell two daughter cells result.Meiosis IIChromatids of each chromosomeare pulled apart - the end result isfour haploid cells, each with halfthe number of chromosomes. Thesedevelop into gametes.
CROSSING OVERImportant event that occurs between each chromosome pair in meiosis IThere is an exchange of segments of DNA and picks up new geneticinformation
INDEPENDENT ASSORTMENTThis occurs when homologous pairs of chromosomes separate at theequator and move towards opposite poles of the cell.VideoMitosisvs Meiosis
FERTILIZATIONThere are more than 8 million combinations possible for these 23 pairsin any egg or sperm cellWhen fertilization occurs, 70 trillion different zygotes are possiblefrom the combination of one sperm cell and one egg cell!
GAMETE FORMATIONMales produce 4 sperm for every round of meiosisFemales produce one egg for each round of meiosis: 3 of the 4 “eggs”produced die off - called polar bodiesAll the cytoplasm, nutrients and energy gets put into one egg
Mitosis vs Meiosis. FERTILIZATION There are more than 8 million combinations possible for these 23 pairs in any egg or sperm cell When fertilization occurs, 70 trillion different zygotes are possible from the combination of one sperm cell and one egg cell! GAMETE FORMATION
Now that you've seen how meiosis works, let's review two key differ-ences between the processes of meiosis and mitosis. Meiosis has two cell divisions. Mitosis has only one cell division. Meiosis results in haploid cells. Mitosis results in diploid cells. On the diagram above, circle the part in the process of meiosis
I II III IV A DNA Replication Mitosis Meiosis Fertilisation B DNA Replication Meiosis 1 Meiosis 2 Fertilisation C Fertilisation Meiosis Mitosis DNA Replication D Mitosis Meiosis 1 Meiosis 2 DNA Replication 4.4 In analysing the number of different bases in a DNA sample, the following result would be consistent with the base-pairing rules: .
Comparison of Meiosis II to Mitosis The events of meiosis II are like those of mitosis except in meiosis II, the nuclei contain the haploid number of chromosomes. At the end of telophase II of meiosis II, there are four haploid daughter cells that are not genetically identical. At the end of mitosis, there are two
Mitosis and Meiosis Outline 1. Key concepts 2. Eukaryotes 3. Overview 4. Cell cycle 5. Mitosis 6. Meiosis 7. Conclusions Key Concepts: 1. The cell cycle includes Interphaseand Mitosis 2. Each DNA molecule, with its attached proteins, is a chromosome 3. Members of the same species have the same number of chromosomes in their cells 4.
Mitosis and meiosis are processes by which animal and plant cells divide. Which statement best describes a difference between mitosis and meiosis? A. Meiosis is a multi-step process. B. Mitosis occurs only in eukaryotic cells. C. Meiosis is used in the repair of an organism.
2. Arrange the remaining chromosomes on the two MEIOSIS sheets, with MEIOSIS I sheet placed above the MEIOSIS II sheet so the arrows flow from sheet to sheet. Remember to show the essential differences between mitosis and meiosis. Be sure to end up with sperm if you are a boy, or an egg with polar bodies if you are a girl.
Cell Division in Sexual Reproduction: Meiosis Meiosis is the mechanism by which eukaryotic cells produce mature sex cells or gametes Meiosis produces four haploid cells (gametes) Meiosis involves partition of both cytoplasmic and nuclear structures Meiosis consists of Meiosis I and Meiosis II. Both phases are followed by .
Meiosis is a form of cell division that halves the number of chromosomes when forming specialized reproductive cells, such as gametes or spores. Meiosis involves two divisions of the nucleus—meiosis I and meiosis II. Before meiosis begins, the DNA in the original cell is replicated. Thus, meiosis starts with homologous chromosomes.
