UNDERSTANDINGS
Mitosis is division of the nucleus into two genetically identical daughter nuclei.
Chromosomes condense by supercoiling during mitosis.
Cytokinesis occurs after mitosis and is different in plant and animal cells.
Interphase is a very active phase of the cell cycle with many processes occurring in the nucleus and cytoplasm.
Cyclins are involved in the control of the cell cycle.
Mutagens, oncogenes and metastasis are involved in the development of primary and secondary tumours.
Chromosomes condense by supercoiling during mitosis.
Cytokinesis occurs after mitosis and is different in plant and animal cells.
Interphase is a very active phase of the cell cycle with many processes occurring in the nucleus and cytoplasm.
Cyclins are involved in the control of the cell cycle.
Mutagens, oncogenes and metastasis are involved in the development of primary and secondary tumours.
INTRODUCTION
Cells divide..........
What is the process happening here? Skin healing.. skin cells form new cells… The cells divide giving rise to new cells Why cells need to divide...
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What happens when a cell divides?
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The nucleus divides first- karyokinesis
Then the cytoplasm divides- Cytokinesis This results in formation of two daughter cells. What would happen if these cells don not stop and keep on dividing…. There will be uncontrolled division leading to forming a mass of cells. This uncontrolled cell division is called ….CANCER The tumour or cancer can happen in any tissue. |
How is the division controlled ?
- Interphase is a very active phase of the cell cycle with many processes occurring in the nucleus and cytoplasm.
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Outline the stages of cell cycle-
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Interphase is an active period in the life of a cell when many metabolic reactions occur, including protein synthesis, DNA replication and an increase in the number of mitochondria and/or chloroplasts.
Interphase includes three phases G1, S and G2 phase.
During the G1 phase there is synthesis of various proteins which allow the cell to specialise. During the S phase the DNA synthesis occurs. During the G2 phase there is enzyme / protein synthesis, biochemical reactions like cell respiration; growth; organelle replication etc. Find out the What is G0 phase? |
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Cyclins are involved in the control of the cell cycle.
Structure of the nucleus
Chromosomes and their organisation.
The replicated DNA condenses to form chromosomes.(supercoiling of chromosomes)
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CLASS GROUP ACTIVITYwatch the video
List the events that are shown in the animation DISCUSS THE CHANGES TAKING PLACE AND TRY TO DIVIDE IT INTO PHASES
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The events that occur in the four phases of mitosis
Events occurring during mitosis1. Prophase-
Supercoiling of chromosomes, chromosomes consist of sister chromatids, formation of mitotic spindle, centrosomes/centrioles move away, nuclear membrane breaks down (late prophase/early metaphase) 2. Metaphase- Attachment of spindle microtubules to centromeres, chromosomes on metaphase plate/equator/centre of cell in metaphase; 3. Anaphase- Parting of (sister) chromatids at beginning, movement of sister chromosomes/chromatids to opposite poles in anaphase; 4. Telophase- Re-formation of nuclear membranes |
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Chromosomes condense by supercoiling during mitosis.
Explain how mitosis produces two genetically identical nuclei.
During interphase DNA produces two copies of genetic material.
Sister chromatids are two identical DNA molecules held together by centromere, these sister chromatids are separated during mitosis to form two genetically identical nuclei.
In prophase chromosomes shorten/thicken/become visible as double-stranded chromosomes.
Chromosomes begin to move towards equator/centre of cell.
During metaphase all chromosomes lined up at equator separate.
At start of anaphase centromeres divide separating sister chromatids.
Separated sister chromatids are pulled to opposite poles.
Nuclear envelope/membrane forms around each set of chromosomes.
Thus results in genetically identical nuclei.
Sister chromatids are two identical DNA molecules held together by centromere, these sister chromatids are separated during mitosis to form two genetically identical nuclei.
In prophase chromosomes shorten/thicken/become visible as double-stranded chromosomes.
Chromosomes begin to move towards equator/centre of cell.
During metaphase all chromosomes lined up at equator separate.
At start of anaphase centromeres divide separating sister chromatids.
Separated sister chromatids are pulled to opposite poles.
Nuclear envelope/membrane forms around each set of chromosomes.
Thus results in genetically identical nuclei.
Growth, embryonic development, tissue repair and asexual reproduction involve mitosis.
Thus it can be stated that mitotic division is responsible for growth of an organism, development of the embryo, repair mechanism and in asexual reproduction.
Multicellular organisms increase their size by increasing their number of cells through mitosis that leads to growth.
Certain eukaryotic organisms may reproduce asexually by mitosis (e.g. vegetative reproduction) i.e. asexual reproduction.
Damaged tissue can recover by replacing dead or damaged cells that helps in healing.
A fertilised egg (zygote) undergoes mitosis and differentiation in order to develop into an embryo.
Multicellular organisms increase their size by increasing their number of cells through mitosis that leads to growth.
Certain eukaryotic organisms may reproduce asexually by mitosis (e.g. vegetative reproduction) i.e. asexual reproduction.
Damaged tissue can recover by replacing dead or damaged cells that helps in healing.
A fertilised egg (zygote) undergoes mitosis and differentiation in order to develop into an embryo.
Mutagens, oncogenes and metastasis are involved in the development of primary and secondary tumours.
Inactive proto-oncogenes become active oncogenes
Application: The correlation between smoking and incidence of cancers.
Skill: Identification of phases of mitosis in cells viewed with a microscope or in a micrograph.
Skill: Determination of a mitotic index from a micrograph.
References-
Damon, Alan et al, Higher level Biology for the IB diploma. Pearson Baccalaureate
Clegg, CJ, Biology for the IB diploma. London: Hodder Murrray, 2007, 978-0340926529
Taylor, Stephan, Science Video resources Wordpress,
Burell, John. Click 4Biology(online)
All picture have been downloaded from Google images for educational purpose only
Damon, Alan et al, Higher level Biology for the IB diploma. Pearson Baccalaureate
Clegg, CJ, Biology for the IB diploma. London: Hodder Murrray, 2007, 978-0340926529
Taylor, Stephan, Science Video resources Wordpress,
Burell, John. Click 4Biology(online)
All picture have been downloaded from Google images for educational purpose only