copyright cmassengale Cell Reproduction Prokaryotes Bacteria Eukaryotes Plants & animals copyright cmassengale
Prokaryotes (Bacteria) REMEMBER: Lack a nucleus Have a single round chromosome Reproduce by binary fission copyright cmassengale
copyright cmassengale Binary Fission Only used by bacteria Cells increase their cell mass slightly DNA & cell components are replicated and sorted in equal parts Each cell divides into 2 daughter cells copyright cmassengale
Binary Fission of Bacterial Cell copyright cmassengale Growth animation
E. Coli Dividing by Binary Fission copyright cmassengale
copyright cmassengale Eukaryotes REMEMBER- Contain a nucleus & membrane bound organelles Continually go through the cell cycle Asexually reproduce cells by mitosis Sexually reproduce new organisms by meiosis copyright cmassengale
copyright cmassengale Cell Cycle Cell cycle is the stages of growth & division NO beginning or end! Interphase G1 Phase S Phase G2 Phase M(itosis) Phase Cytokinesis copyright cmassengale
Interphase – Resting Stage Cells carrying on normal activities i.e metabolism Individual chromosomes aren’t visible Three subphases (G1, S, G2) Two checkpoints to control growth
copyright cmassengale Interphase copyright cmassengale
copyright cmassengale G1 Phase First growth stage Cell increases in size Cell prepares to copy its DNA G1/S Checkpoint at the end copyright cmassengale
G1/S checkpoint G1/S checkpoint is most critical primary decision point “restriction point” if cell receives “GO” signal, it divides internal signals: cell growth (size), cell nutrition external signals: “growth factors” if cell does not receive signal, it exits cycle & switches to G0 phase non-dividing, working state
G0 phase G0 phase non-dividing, differentiated state most human cells in G0 phase liver cells in G0, but can be “called back” to cell cycle by external cues nerve & muscle cells highly specialized arrested in G0 & can never divide
copyright cmassengale S(ynthesis) Phase Copying of all of DNA’s instructions copyright cmassengale
Duplicated Chromosome copyright cmassengale
copyright cmassengale G2 Phase Second growth stage Replicates organelles Proteins needed for cell division (M phase) produced G2/M Checkpoint to ensure DNA has been properly synthesized and cell is ready copyright cmassengale
copyright cmassengale M Phase Cell growth & protein production stop Cell’s energy used to make 2 IDENTICAL daughter cells Called mitosis or karyokinesis (nuclear division) copyright cmassengale
copyright cmassengale Stages of Mitosis Preparation for division Separation of Chromosomes copyright cmassengale
Cells Undergoing Mitosis copyright cmassengale
Prep for Division Must remove barriers like nucleus Neatly coil up chromosomes so they can easily be separated Attach machinery/proteins necessary to divide chromosomes evenly (spindle fibers) Spindle checkpoint to make sure everything is connected properly
copyright cmassengale Mitotic Spindle copyright cmassengale
copyright cmassengale Human Chromosomes copyright cmassengale
Separation of chromosomes SISTER CHROMATIDS are pulled apart at centromere by the spindle fibers Shortest stage copyright cmassengale
copyright cmassengale Cytokinesis Division of cytoplasm Reform nucleus, recycle proteins used, etc Forms a cell plate (plants) or cleavage furrow (animals) Eventually forms two, identical daughter cells copyright cmassengale
copyright cmassengale Plant Animal copyright cmassengale
Frequency of cell division Frequency of cell division varies by cell type embryo cell cycle < 20 minute skin cells divide frequently throughout life 12-24 hours cycle liver cells retain ability to divide, but keep it in reserve divide once every year or two mature nerve cells & muscle cells do not divide at all after maturity permanently in G0
Cancer When a cell fails checkpoints BUT continues to divide – generally, cancer!! Proto-oncogenes – genes that that control the cell cycle Oncogenes – genes that mutated and no longer control the cell cycle Mutations are caused by lots of things – chemicals, UV radiation, genetics, heat, etc