Cell Reproduction Prokaryotes Bacteria Eukaryotes Plants animals copyright
Cell Reproduction Ø Ø Prokaryotes Bacteria Eukaryotes Plants & animals copyright cmassengale
Prokaryotes (Bacteria) Ø REMEMBER: Ø Lack a nucleus Ø Have a single round chromosome Ø Reproduce by binary fission copyright cmassengale
Binary Fission Only used by bacteria Ø Cells increase their cell mass slightly Ø DNA & cell components are replicated and sorted in equal parts Ø Each cell divides into 2 daughter cells Ø copyright cmassengale
Binary Fission of Bacterial Cell copyright cmassengale Growth animation
E. Coli Dividing by Binary Fission copyright cmassengale
Eukaryotes Ø REMEMBERØ Contain a nucleus & membrane bound organelles Ø Continually go through the cell cycle Ø Asexually reproduce cells by mitosis Ø Sexually reproduce new organisms by meiosis copyright cmassengale
Cell Cycle Cell cycle is the stages of growth & division Ø NO beginning or end! Ø Interphase Ø Ø G 1 Phase Ø S Phase Ø G 2 Phase Ø M(itosis) Ø Phase Cytokinesis copyright cmassengale
Interphase – Resting Stage Ø Cells carrying on normal activities i. e metabolism Ø Individual chromosomes aren’t visible Ø Three subphases (G 1, S, G 2) Ø Two checkpoints to control growth
Interphase copyright cmassengale
G 1 Phase Ø First growth stage Ø Cell increases in size Ø Cell prepares to copy its DNA Ø G 1/S Checkpoint at the end copyright cmassengale
G 1/S checkpoint l G 1/S checkpoint is most critical – primary decision point l “restriction point” – if cell receives “GO” signal, it divides internal signals: cell growth (size), cell nutrition l external signals: “growth factors” l – if cell does not receive signal, it exits cycle & switches to G 0 phase l non-dividing, working state
l G 0 phase – non-dividing, differentiated state – most human cells in G 0 phase § liver cells § in G 0, but can be “called back” to cell cycle by external cues § nerve & muscle cells § highly specialized § arrested in G 0 & can never divide
S(ynthesis) Phase Ø Copying of all of DNA’s instructions copyright cmassengale
Duplicated Chromosome copyright cmassengale
G 2 Phase Ø Second growth stage Ø Replicates organelles Ø Proteins needed for cell division (M phase) produced Ø G 2/M Checkpoint to ensure DNA has been properly synthesized and cell is ready copyright cmassengale
M Phase Ø Cell growth & protein production stop Ø Cell’s energy used to make 2 IDENTICAL daughter cells Ø Called mitosis or karyokinesis (nuclear division) copyright cmassengale
Stages of Mitosis Ø Preparation for division Ø Separation of Chromosomes copyright cmassengale
Cells Undergoing Mitosis copyright cmassengale
Prep for Division l Must remove barriers like nucleus l Neatly coil up chromosomes so they can easily be separated l Attach machinery/proteins necessary to divide chromosomes evenly (spindle fibers) l Spindle checkpoint to make sure everything is connected properly
Mitotic Spindle copyright cmassengale
Human Chromosomes copyright cmassengale
Separation of chromosomes l SISTER CHROMATIDS are pulled apart at centromere by the spindle fibers l Shortest stage copyright cmassengale
Cytokinesis Ø Division of cytoplasm Ø Reform nucleus, recycle proteins used, etc Ø Forms a cell plate (plants) or cleavage furrow (animals) Ø Eventually forms two, identical daughter cells copyright cmassengale
Plant Animal copyright cmassengale
Frequency of cell division l Frequency of cell division varies by cell type – embryo l cell cycle < 20 minute – skin cells divide frequently throughout life l 12 -24 hours cycle l – liver cells retain ability to divide, but keep it in reserve l divide once every year or two l – mature nerve cells & muscle cells do not divide at all after maturity l permanently in G 0 l
Cancer l When a cell fails checkpoints BUT continues to divide – generally, cancer!! l Proto-oncogenes – genes that control the cell cycle l Oncogenes – genes that mutated and no longer control the cell cycle l Mutations are caused by lots of things – chemicals, UV radiation, genetics, heat, etc
- Slides: 26