- Slides: 13
Mitosis • 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)
Prophase • During Prophase the chromosomes containing two identical chromatids condense in to defined units, allowing organised and equal segregation into daughter cells. • Also the nuclear envelope breaks down allowing microtubules to interact with the chromosomes.
Metaphase • During Metaphase the chromosomes congregate across the middle of the cell. • Tubular structures called spindles start to grow from the poles towards the chromosomes ready to attach and pull the chromosomes apart
Anaphase • During Anaphase the chromosomes are split up into sister chromatids and moved to separate poles of the cells by spindles. • Once separated the nuclear membrane reforms around the chromatids at each pole
Telophase • After sister chromatids are separated and nuclear membranes are reformed
Cytokinesis • The cell’s cytoplasm goes on to divide in half • Each new cell retains a copy of the parent cell’s genetic information.
Stages of mitosis: match them up 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
The cell cycle interphase G 1: cytopla s mic div Mitotic phase nuclear division Growth of daughter cell Duplication of organelles other than nucleus telophase anaphase metaphase prophase S: Replication of DNA G 2: Cell checks DNA and makes any repairs. Cell prepares for division
Cancer is caused by a growth disorder of the cells. It is the result of a gene mutation that regulate the cell cycle thereby causing uncontrolled growth and division of cells. ‘Mutant cells’ that form from this uncontrolled division are usually both structurally and functionally different from normal cells. Some of these cells will die but those that don’t keep dividing forming tumours. A tumour becomes cancerous (malignant) when it invades other cells, tissues or organs If the cell cycle is interrupted then it should result in stopping the tumour from growing. The drugs given to patients will prevent DNA from replicating and also inhibit metaphase so the spindle doesn’t form.
Summary • 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 and cytplasmic division (cytokinesis). • Cancer is caused by mutation of genes that regulate the cell cycle and treatment is designed to inhibit cell division.
Questions 1. 2. 3. 4. 5. What is created through mitosis? What is the stage of the cell cycle in which the cell is not dividing? Describe the main events of prophase What happens during cytokinesis? Where does the energy for anaphase come from? Exam question (part of) The image above shows one cell a student saw in onion tissue. The student concluded that the cell in the image above was in the anaphase stage of mitosis. Was she correct? Give two reasons for your answer.