Topic 3.2 Cells Specification 3.2.3 All cells arise from other cells Lesson 1 3.2.2 All cells arise from other cell • • • • Within multicellular organisms, not all cells retain the ability to divide. Eukaryotic cells that do retain the ability to divide show a cell cycle. DNA replication occurs during the interphase of the cell cycle. Mitosis is the part of the cell cycle in which a eukaryotic cell divides to produce two daughter cells, each with the identical copies of DNA produced by the parent cell during DNA replication. • The behaviour of chromosomes during interphase, prophase, metaphase, anaphase and telophase of mitosis. The role of spindle fibres attached to centromeres in the separation of chromatids. • Division of the cytoplasm (cytokinesis) usually occurs, producing two new cells. Students should be able to: • recognise the stages of the cell cycle: interphase, prophase, metaphase, anaphase and telophase (including cytokinesis) • explain the appearance of cells in each stage of mitosis. • Mitosis is a controlled process. Uncontrolled cell division can lead to the formation of tumours and of cancers. Many cancer treatments are directed at controlling the rate of cell division. • Binary fission in prokaryotic cells involves: • replication of the circular DNA and of plasmids • division of the cytoplasm to produce two daughter cells, each with a single copy of the circular DNA and a variable number of copies of plasmids. • Being non-living, viruses do not undergo cell division. Following injection of their nucleic acid, the infected host cell replicates the virus particles. Starter – which of these terms can you remember from the 5ths? • https://quizlet.com/62633263/igcse-biologyvariation-and-inheritance-flash-cards/ • Flash cards game on quizlet – search: • User: laparkes • IGCSE Biology – Variation and Inheritance Chromosomes – a reminder Mitosis • Eukaryotic cells. Not all cells retain this ability – some only do it once – many specialised cells for example. • Parent cell divides to produce 2 daughter cells. • Both contain complete copy of parent DNA and are thus genetically identical….when may they not be identical? • Mutation only • When a cell is not dividing it is between dividing stages and is said to be in Interphase. The cell cycle. • The cell cycle is the life of a cell from one division to the next. • It has three main stages ~ interphase, mitosis and cytokinesis (marginal time so not displayed on time continuum) Interphase. • Generally 90% of the cell cycle is spent in interphase. • The cell does what is has to do i.e. respire, secrete hormone, transmit nerve impulses, contracts, synthesizes molecules • There are 3 stages to interphase 3 stages of interphase. • Growth phase (G1) ~ the cell grows back to its original size, genes are expressed, organelles are replicated. Cytoplasm increases. If the cell is not going to divide again, it remains in this phase (e.g nerve cells & muscle cells). • Synthesis phase (S) ~ DNA & histones are replicated prior to mitosis. This stage may take a few hours. • Growth phase (G2) ~ spindle fibres are synthesized ready for mitosis • Followed by Mitosis (M) and Cytokinesis (C). Control of the cell cycle • When young – frequent due to growth but as you age it slows and can stop in some tissues. • Control by chemical signals produced by genes – Cyclins, these control transition between stages. • The cyclins build up an attach to CDKs (cyclin dependent kinase enzymes). • The cyclin CDK complex changes other proteins to bring about the next stage in the cycle. • If you are intersted: • http://en.wikipedia.org/wiki/Oncogene Mitosis is involved in: DIFFERENTIATION – cells change to give groups of specialised cells, then divide by mitosis to give tissues GROWTH – involves an increase in size through the division of cells by mitosis CELL REPLACEMENT/REPAIR – many cells within a multicellular organism are constantly dying and being replaced by mitosis ASEXUAL REPRODUCTION – asexual reproduction in certain plants and lower eukaryotic animals, involves the process of mitosis Budding in this species of Hydra is a form of asexual reproduction; new individuals are produced as outgrowths of the parent by the process of mitosis Homework • To use the app – Animal histology by carolina (free on the app store – lite version, that is all that is needed). • Spend some time studying the stages of mitosis (flipped lesson) from the app. • Make notes from the YouTube video: • https://www.youtube.com/watch?v=L0k-enzoeOM Mitosis is a continuous process but for convenience of description is divided into FOUR MAIN STAGES: Prophase Please Metaphase Make Anaphase Another Telophase Two The following slides describe the process of mitosis in a hypothetical animal cell that possesses two pairs of homologous chromosomes Topic 3.2 Cells Specification 3.2.3 All cells arise from other cells Lesson 2 3.2.2 All cells arise from other cell • • • • Within multicellular organisms, not all cells retain the ability to divide. Eukaryotic cells that do retain the ability to divide show a cell cycle. DNA replication occurs during the interphase of the cell cycle. Mitosis is the part of the cell cycle in which a eukaryotic cell divides to produce two daughter cells, each with the identical copies of DNA produced by the parent cell during DNA replication. • The behaviour of chromosomes during interphase, prophase, metaphase, anaphase and telophase of mitosis. The role of spindle fibres attached to centromeres in the separation of chromatids. • Division of the cytoplasm (cytokinesis) usually occurs, producing two new cells. Students should be able to: • recognise the stages of the cell cycle: interphase, prophase, metaphase, anaphase and telophase (including cytokinesis) • explain the appearance of cells in each stage of mitosis. • Mitosis is a controlled process. Uncontrolled cell division can lead to the formation of tumours and of cancers. Many cancer treatments are directed at controlling the rate of cell division. • Binary fission in prokaryotic cells involves: • replication of the circular DNA and of plasmids • division of the cytoplasm to produce two daughter cells, each with a single copy of the circular DNA and a variable number of copies of plasmids. • Being non-living, viruses do not undergo cell division. Following injection of their nucleic acid, the infected host cell replicates the virus particles. Playdough Topic 3.2 Cells Specification 3.2.3 All cells arise from other cells Lesson 3 3.2.2 All cells arise from other cell • • • • Within multicellular organisms, not all cells retain the ability to divide. Eukaryotic cells that do retain the ability to divide show a cell cycle. DNA replication occurs during the interphase of the cell cycle. Mitosis is the part of the cell cycle in which a eukaryotic cell divides to produce two daughter cells, each with the identical copies of DNA produced by the parent cell during DNA replication. • The behaviour of chromosomes during interphase, prophase, metaphase, anaphase and telophase of mitosis. The role of spindle fibres attached to centromeres in the separation of chromatids. • Division of the cytoplasm (cytokinesis) usually occurs, producing two new cells. Students should be able to: • recognise the stages of the cell cycle: interphase, prophase, metaphase, anaphase and telophase (including cytokinesis) • explain the appearance of cells in each stage of mitosis. • Mitosis is a controlled process. Uncontrolled cell division can lead to the formation of tumours and of cancers. Many cancer treatments are directed at controlling the rate of cell division. • Binary fission in prokaryotic cells involves: • replication of the circular DNA and of plasmids • division of the cytoplasm to produce two daughter cells, each with a single copy of the circular DNA and a variable number of copies of plasmids. • Being non-living, viruses do not undergo cell division. Following injection of their nucleic acid, the infected host cell replicates the virus particles. Watch • https://www.youtube.com/watch?v=QVCjdNxJreE Article • Read together article on cancer and the cell cycle Questions Topic 3.2 Cells Specification 3.2.3 All cells arise from other cells Lesson 4 3.2.2 All cells arise from other cell • • • • Within multicellular organisms, not all cells retain the ability to divide. Eukaryotic cells that do retain the ability to divide show a cell cycle. DNA replication occurs during the interphase of the cell cycle. Mitosis is the part of the cell cycle in which a eukaryotic cell divides to produce two daughter cells, each with the identical copies of DNA produced by the parent cell during DNA replication. • The behaviour of chromosomes during interphase, prophase, metaphase, anaphase and telophase of mitosis. The role of spindle fibres attached to centromeres in the separation of chromatids. • Division of the cytoplasm (cytokinesis) usually occurs, producing two new cells. Students should be able to: • recognise the stages of the cell cycle: interphase, prophase, metaphase, anaphase and telophase (including cytokinesis) • explain the appearance of cells in each stage of mitosis. • Mitosis is a controlled process. Uncontrolled cell division can lead to the formation of tumours and of cancers. Many cancer treatments are directed at controlling the rate of cell division. • Binary fission in prokaryotic cells involves: • replication of the circular DNA and of plasmids • division of the cytoplasm to produce two daughter cells, each with a single copy of the circular DNA and a variable number of copies of plasmids. • Being non-living, viruses do not undergo cell division. Following injection of their nucleic acid, the infected host cell replicates the virus particles. Watch • https://www.youtube.com/watch?v=alQt-0rTQRQ • 0mins to 2.45 mins • Discuss • Own notes Viruses • Not cells, not alive. • Have to replicate in a host. • https://www.khanacademy.org/science/high-schoolbiology/hs-human-body-systems/hs-the-immunesystem/v/viral-replicaiton-lytic-vs-lysogenic (5 mins lytic vs lysogenic) • Inject genetic material into host. Host then expresses this material • Variety of methods DNA, +/- ssRNA, RNA retrovirus. • 8 mins (deliberately short) research one of the above. Then discuss as a class. Antiviral drugs • Why is it so difficult to treat viral infections? • Why do viruses make you ill?
