Presentation on theme: "Cell Cycle and Mitosis a.k.a. Cell Reproduction"— Presentation transcript:
1 Cell Cycle and Mitosis a.k.a. Cell Reproduction Biology is the only subject inwhich multiplication is the samething as division
2 Introduction All organisms start with a single cell. All new cells are produced from other, already existing cells.Millions of cell divisions take place in our bodies every day to replace the cells that have diedCell TypeApproximate Life SpanSkin Cells2 weeksRed Blood Cells4 monthsLiver CellsdaysIntestine-internal lining4-5 daysIntestine-muscles and other tissue16 yearsSource: Spaulding et al., Cell 122:1.
3 Type of Cells it occurs in 3 Types of Cell DivisionType of Cell DivisionType of Cells it occurs inFunctionBinary FissionProkaryotesAsexual ReproductionMitosisEukaryotesGrowth of IndividualRepair/Maintenance of TissuesMeiosisSexual Reproduction
4 Binary fission Asexual reproduction of a Prokaryotic cell Bacteria (Ex E. coli = every 20 minutes)How many bacteria will result from 1 bacteria 7 hours (optimal conditions)? 1 million!
5 Binary Fission Begins with the duplication of the genetic material A plasma membrane splits the cell in two, with each side containing a single copy of the DNAThe resulting two daughter cells replace the single parent cell and are genetically identical
6 Eukaryotes Use Mitosis to Generate Identical Daughter Cells Multiphase process in which the cell divides from 1 parent cell to 2 identical daughter cells.Occurs in all cells except reproductive cellsMitosis is how asexual cell are replicated.Meiosis is how sex cells are produced (we will look at this process later in the term)
7 The Cell Cycle Interphase is not part of mitosis!! This is when the cell is doing its “everyday” jobs and getting ready for mitosisInterphase is divided into 3 phases:G1 = 1st Gapcell doing its “everydayjob”cell growsS = DNA Synthesiscopies chromosomesG2 = 2nd Gapprepares for divisionproduces organelles, proteins, membranesLength of G1 differs the most from cell type to cell typeS, G2 and mitosis take about 12 hours in human cellsIn embryos and children go through the cell cycle faster
8 The Cell Cycle Many adult cells enter a non-dividing phase called G0 The G0 phase can last from a few days to the lifetime of the organismEx: liver cells stay in G0 for approximately a year, then reenter the cycle
9 Organization of Genetic Material For equal division of the DNA to occur it has to be organizedIn interphase each DNA double helix is packaged with special proteins to form long strands of chromatinChromatin is further compacted during mitosis to formchromosomesDNA PackagingDNA during InterphaseDNA during Mitosis
10 Organization of Genetic Material One ChromosomeDNA is replicated during S phase, resulting in two identical pieces of DNA, known as sister chromatidsEach human cell has twice the usual amount of DNA at the end of S phase and the start of mitosisThe identical sister chromatids are held together at a region called the centromere
11 The Karyotype Describes All the Chromosomes in a Nucleus Every species has its own characteristic number of chromosomesThe display of all the chromosomes in a somatic (non-sexual) cell is called the karyotypeEach of us has two of each chromosome, one from mom and one from dad.This pair of chromosomes, one from mom and one from dad, are similar but not identicalThey are called homologous chromosomes
12 Karyotypes Before and After S-phase of Cell Cycle Before S-PhaseAfter S-Phase
13 Karyotype of The Human Genome Let’s not get Chromosomes, Homologous Chromosomes, and Sister Chromatids Confused!!Copied Homologous ChromosomesHomologous ChromosomesThis is part of a karyotype looking at just chromosome 1Sister Chromatids
14 Prophase Metaphase Anaphase Telophase Video 4 Stages of Mitosis:Prophase Metaphase Anaphase Telophase Video
15 Prophase Beginning of mitosis DNA compacts into chromosomes Centrosomes appear and begin to move to opposite ends of cell making the poles of the cellThe nuclear envelope breaks downThe mitotic spindle forms. It is made up of microtubules attached to each centrosomeWhat is a microtubule? Remember from cytoskeleton?Centrosomes (centro- center, some- body)
16 MetaphaseSister chromatids attach to the spindle fibers at the centromere through the kinetochoreThe kinetochores are patches of proteins that attaches to the microtubulesEach centromere has two kinetochores that attach to the spindle fibers, one from each centrosomeThis causes the chromosomes to line up on the metaphase plate
17 AnaphaseSister Chromatids separate and begin to move to opposite ends of the cellThe centrosomes shorten the spindle fibers dividing the sister chromosomes and bringing them to opposite side of the cellEach chromatid is now considered a new chromosome
18 Telophase Begins when the new chromosomes reach the centrosome The spindle fibers break downTwo new nuclei form and the nuclear envelope forms around the chromosomes at each pole of the cellChromosomes appear as chromatinAfter telophase cytokinesis occurs
19 Cytokinesis in Animal Cells Not considered a phase in mitosisFollows telophaseThe cell membrane moves inward to create two daughter cellsOccurs at the metaphase plate
20 Cytokinesis in Plant Cells Since plants have cell walls they also have to build this between daughter cells.Vesicles containing cell wall components move to the metaphase plate where the cell wall forms
21 How can you remember the order???? Answer this question....Where would you like your cat or dog to pee?On a PMAT of course
22 The Cell Cycle Is Highly Regulated Cells divide in response to internal and external signalsIn humans, cell cycle regulatory proteins are activated by external signals to divide, advancing the cell from G1 to S phase and initiating DNA replicationCell cycle regulatory proteins can stop or pause the cell cycle if conditions are not favorable for cell divisionWhat is this condition called?What happens when the cell does not stop at a checkpoint?
23 Cancer 6 key mutations Turn on cell division Ignore checkpoints Turn on promoter genesIgnore checkpointsTurn off suppressor genesAvoid programed cell deathTurn off “suicide” genesUnlimited divisionsTurn on chromosome maintenance genesPromotes blood vessel growthTurn on blood vessel genesCell attachment, anchor and density dependence genesTurn off touch censor gene