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AQA Biology AS Level Unit 2 Meiosis, Mitosis and the Cell Cycle Outcomes: • Know that cell division by meiosis results in the formation of gametes. • Can describe the importance of meiosis in creating variation by independent assortment of chromosomes and crossing over. • Know that cell division by mitosis results in an increase in number of identical cells for growth and repair. • Identify and name the stages of mitosis in diagrams and photomicrographs. • Describe the cell cycle and relate it to an understanding of cancer and its treatment. Replication of chromosomes occurs prior to division Homologous chromosomes centromere chromatids chromosome Meiosis consists of two divisions Meiosis 1 Meiosis 2 Gametes are formed by meiosis: Homologous chromosomes associate Outcomes: • Know that cell division by meiosis results in the formation of gametes. • Describe the importance of meiosis in creating variation by independent assortment of chromosomes and crossing over. • Know that cell division by mitosis results in an increase in number of identical cells for growth and repair. • Identify and name the stages of mitosis in diagrams and photomicrographs. • Describe the cell cycle and relate it to an understanding of cancer and its treatment. Independent segregation increases variation maternal paternal Random assortment in meiosis I Random assortment in meiosis II or maternal paternal Random assortment in meiosis I Random assortment in meiosis II Crossing over increases variation recombinant chromosome chiasma In the first division of meiosis the homologous chromosomes associate Crossing over increases variation B B b b G g G g B, G B, g b, G b, g All gametes have a different combination of alleles on the chromosomes Outcomes: • Know that cell division by meiosis results in the formation of gametes. • Can describe the importance of meiosis in creating variation by independent assortment of chromosomes and crossing over. • Know that cell division by mitosis results in an increase in number of identical cells for growth and repair. • Identify and name the stages of mitosis in diagrams and photomicrographs. • Describe the cell cycle and relate it to an understanding of cancer and its treatment. Mitosis produces two identical daughter cells. metaphase prophase anaphase interphase telophase cytoplasmic division (cytokinesis) Stages of mitosis M I T O S I S interphase Chromosomes appear, nucleus disappears prophase Chromatids pulled to poles metaphase Chromosomes invisible; DNA replicates anaphase Cytoplasmic division telophase Chromosomes at equator, spindle forms cytokinesis Chromatids at poles, nucleus reforms Outcomes: • Know that cell division by meiosis results in the formation of gametes. • Can describe the importance of meiosis in creating variation by independent assortment of chromosomes and crossing over. • Know that cell division by mitosis results in an increase in number of identical cells for growth and repair. • Identify and name the stages of mitosis in diagrams and photomicrographs. • Describe the cell cycle and relate it to an understanding of cancer and its treatment. The cell cycle interphase G1: Growth of daughter cell Duplication of organelles other than nucleus nuclear division S: anaphase Replication of DNA G2: Cell checks DNA and makes any repairs. Cell prepares for division Cancer Summary • Meoisis produces haploid gametes that are genetically different. Variation is further increased by independent segregation of chromosomes and crossing over forming recombinant chromosomes. • Mitosis is the nuclear division which produces 2 genetically identical, diploid cells. It consists of prophase, metaphase, anaphase and telophase. • Cell cycle consists of interphase, nuclear division (mitosis or meiosis) and cytplasmic division (cytokinesis). • Cancer is caused by mutation of genes that regulate the cell cycle and treatment is designed to inhibit cell division.