Topic 2 Cells Mitosis Meiosis Part 2A PDF

What will I learn 1. Explain the Cell Theory. 2. Differentiate eukaryotic from prokaryotic cells. 3. Explain the structure and functions of cell membrane and organelles. 4. Describe the events that occur during mitosis and meiosis. Cell Mitosi Meiosi Cycle...

What will I learn 1. Explain the Cell Theory. 2. Differentiate eukaryotic from prokaryotic cells. 3. Explain the structure and functions of cell membrane and organelles. 4. Describe the events that occur during mitosis and meiosis. Cell Mitosi Meiosi Cycle s s Cell Cycle Cell Cycle in Eukaryotes  A series of events that take place in a cell as it grows and divides into 2 identical daughter cells  Two periods:  Interphase – cells increase in size and grow. Chromosomes are replicated.  Cell division – during which a parent cell divides into daughter cells: Mitosis & Cytokinesis Cell Cycle G1 + S + G2 = Cell Cycle in Eukaryotes INTERPHASE  Two periods (4 stages): *  Interphase – *  G1 phase – protein synthesis, cells increase in size, generate ATP This image comes from the archive of Dr Josef Reischig, CSc  S phase – DNA replication  Ensure cells have 2x DNA before dividing  G2 phase – More protein synthesis, further increase in size, generate ATP  Cell division –  M phase (cell division)  Mitosis (nuclear division)  Cytokinesis (cytoplasmic division) MITOSIS AND MEIOSIS  Mitosis Mitosis (Nuclear Division)  Before nuclear division begins, DNA has to be replicated so as to double the DNA content in the nucleus.  Why? So that the 2 new daughter cells will have the original amount of DNA, identical to the parent cell  Important term: Chromosomes Chromosomes are found in the nucleus. Chromosomes are made of DNA wrapped around proteins to form an X-shaped structure). Sections of chromosomes are called genes. DNA: Genetic code that contains all the information needed to build and maintain an organisms. How many chromosomes do WE have? https://rsscience.com/ chromosome/ Important term: Chromosomes vs Chromatids Homologous Homologous chromosomes chromosomes DNA Centromere replication These 2 are sister These 2 are sister chromatids chromatids Homologous Sister chromatids are chromosomes are Same size/length Same size/length Carry same genes Carry same genes Exact duplication of respective 1 from father, 1 from homologous chromosome mother  Stages of Mitosis  Consists of 4 main stages: 1. Prophase Remember: DNA already 2. Metaphase doubled to 2 x original during 3. Anaphase the S phase 4. Telophase Specialized region of cell that includes a pair of centrioles. INTERPHA Stages of Mitosis: PROPHASE Each chromosome = Two identical sister chromatids (joined at One chromatid centromere) Centriole pairs move to opposite ends Sister chromatids of cell Centromere Nucleolus disappears One chromosome Nuclear envelope breaks up Spindle fibres form Asters Chromosomes Nuclear envelope INTERPHA Spindle fibres breaks up PROPHA  Metapha se: Meet in the Stages of Mitosis: METAPHASE Middle Chromosomes line up around the equator (‘centre’) of the spindle One chromatid The centromere of each chromosome is attached to a spindle Sister chromatids fibre Centromere One chromosome Centromere Chromosomes Spindle fibres PROPHA METAPHA  Anaphas e: moving Stages of Mitosis: ANAPHASE Apart Each centromere splits Sister chromatids are pulled apart to One chromatid opposite poles of the cell by the spindle fibres Sister chromatids Separated chromatids = daughter Centromere chromosomes One chromosome METAPHA ANAPHAS Stages of Mitosis: TELOPHASE Spindle fibres break down New nuclear envelope forms at each One chromatid pole, around the chromosomes A nucleolus forms within each Sister chromatids nucleus Centromere Chromosomes uncoil and lengthen One chromosome to form thin chromatin threads ANAPHAS E TELOPHAS Cytokinesis Division of cytoplasm Furrows appear in the cell membrane between the 2 daughter nuclei Formation of 2 separate daughter cells Number of chromosomes in each daughter cells is EXACTLY the same as in the parent cell. Cytoplasm Summary – mitosis:  Many eukaryotic cells are in a cyclical looped event called the Cell Cycle  G1→ S → G2 → M o Interphase: cells are getting ready to undergo cell division o followed by mitosis and cytokinesis  Mitosis (nuclear division) o Prophase o Metaphase o Anaphase o Telophase  Cytokinesis (cytoplasm division)