5.1.3
Mitosis
Stages of Mitosis
Stages of Mitosis
In mitosis, chromosomes go through interphase, prophase, metaphase, anaphase and telophase in order to produce genetically identical cells.


Interphase
Interphase
- The cell prepares to divide.
- DNA is replicated by semi-conservative replication. There is now two copies of every chromosome.
- The organelles are also replicated.
- More ATP is produced to be used in cell division.


Prophase
Prophase
- The nuclear envelope and the nucleolus break down. Chromosomes are left floating in the cytoplasm.
- The chromosomes coil more tightly and become shorter and fatter. They can be seen under a light microscope.
- Small protein bundles called centrioles move to opposite poles of the cell.
- Microtubules form the mitotic spindle between the centrioles.


Metaphase
Metaphase
- The chromosomes line up along the mid-line of the cell.
- In metaphase, the chromosomes are maximally condensed.
- They are attached to the spindle by the centromere.


Anaphase
Anaphase
- The chromosomes break into two chromatids. The sister chromatids separate at the centromere.
- The spindles contract and pull the chromatids to each pole of the cell.


Telophase
Telophase
- The chromatids reach the opposite poles and begin to decondense (unravel), becoming chromosomes again.
- Nuclear envelopes form around the chromosomes so there are now two nuclei.
- The cytoplasm splits and two daughter cells are formed. The daughter cells are identical to the original cell and to each other.
- The cell cycle starts again.


Way to remember the stages:
Way to remember the stages:
- I (interphase).
- Picked (prophase).
- My (metaphase).
- Apples (anaphase).
- Today (telophase).
Preparation of Stained Squashes of Cells from Root Tips
Preparation of Stained Squashes of Cells from Root Tips
Only a few cells are able to continue dividing in a multicellular organism. In plants, the growing tips of roots and shoots contain meristem tissue that can divide by mitosis for growth.


1) Sample preparation
1) Sample preparation
- Wear gloves and use forceps to handle the tips.
- Root tips must be sprouting (actively growing).
- Place into 5 M hydrochloric acid.
- After 5 minutes, rinse the tips in cold water in a watch glass.


2) Cut the root tips
2) Cut the root tips
- Using a sharp scalpel, cut root tips that are 2 mm long.
- Place a root tip onto a microscope slide. Ensure the slide is clean to reduce the chances of artefacts.


3) Staining
3) Staining
- Carefully add 2-3 drops of stain and leave for two minutes.
- Use a mounted needle to spread out the root tips into a thin layer.
- Place a coverslip over the top of the tips.


4) Squashing
4) Squashing
- Squash down by applying force to the cover slip. This could be with the flat end of a pencil, or the slide could be covered with a paper towel and pressed.
- Force must be vertical or the cover slip may break and cause injury.


5) Viewing the sample
5) Viewing the sample
- Place the slide on the microscope stage using the lowest power lens.
- Focus the lens on the sample using first the coarse control and then the fine control.
- Move the slide to see the range of cells. The cells closer to the tip will be those more actively dividing.
- On a lens power of 400x, it should be possible to clearly see the chromosomes in the dividing cells.
1Cell Structure
1.1Cell Structure
1.1.1Studying Cells - Microscopes
1.1.2Introduction to Eukaryotic & Prokaryotic Cells
1.1.3Ultrastructure of Eukaryotic Cells
1.1.4Ultrastructure of Eukaryotic Cells 2
1.1.5Ultrastructure of Eukaryotic Cells 3
1.1.6Prokaryotic Cells
1.1.7Viruses
1.1.8End of Topic Test - Cell Structure
1.1.9Exam-Style Question - Microscopes
1.1.10A-A* (AO2/3) - Cell Structure
2Biological Molecules
2.1Testing for Biological Modules
2.2Carbohydrates & Lipids
2.3Proteins
3Enzymes
4Cell Membranes & Transport
4.1Biological Membranes
5The Mitotic Cell Cycle
6Nucleic Acids & Protein Synthesis
6.1Nucleic Acids
7Transport in Plants
8Transport in Mammals
8.1Circulatory System
8.2Transport of Oxygen & Carbon Dioxide
9Gas Exchange
9.1Gas Exchange System
10Infectious Diseases
10.1Infectious Diseases
10.2Antibiotics
11Immunity
12Energy & Respiration (A2 Only)
13Photosynthesis (A2 Only)
14Homeostasis (A2 Only)
14.1Homeostasis
14.2The Kidney
14.3Cell Signalling
14.4Blood Glucose Concentration
14.5Homeostasis in Plants
15Control & Coordination (A2 Only)
15.1Control & Coordination in Mammals
15.1.1Neurones
15.1.2Receptors
15.1.3Taste
15.1.4Reflexes
15.1.5Action Potentials
15.1.6Saltatory Conduction
15.1.7Synapses
15.1.8Cholinergic Synnapses
15.1.9Neuromuscular Junction
15.1.10Skeletal Muscle
15.1.11Sliding Filament Theory Contraction
15.1.12Sliding Filament Theory Contraction 2
15.1.13Menstruation
15.1.14Contraceptive Pill
15.2Control & Co-Ordination in Plants
16Inherited Change (A2 Only)
16.1Passage of Information to Offspring
16.2Genes & Phenotype
17Selection & Evolution (A2 Only)
17.2Natural & Artificial Selection
18Classification & Conservation (A2 Only)
18.1Biodiversity
18.2Classification
19Genetic Technology (A2 Only)
19.1Manipulating Genomes
19.2Genetic Technology Applied to Medicine
19.3Genetically Modified Organisms in Agriculture
Jump to other topics
1Cell Structure
1.1Cell Structure
1.1.1Studying Cells - Microscopes
1.1.2Introduction to Eukaryotic & Prokaryotic Cells
1.1.3Ultrastructure of Eukaryotic Cells
1.1.4Ultrastructure of Eukaryotic Cells 2
1.1.5Ultrastructure of Eukaryotic Cells 3
1.1.6Prokaryotic Cells
1.1.7Viruses
1.1.8End of Topic Test - Cell Structure
1.1.9Exam-Style Question - Microscopes
1.1.10A-A* (AO2/3) - Cell Structure
2Biological Molecules
2.1Testing for Biological Modules
2.2Carbohydrates & Lipids
2.3Proteins
3Enzymes
4Cell Membranes & Transport
4.1Biological Membranes
5The Mitotic Cell Cycle
6Nucleic Acids & Protein Synthesis
6.1Nucleic Acids
7Transport in Plants
8Transport in Mammals
8.1Circulatory System
8.2Transport of Oxygen & Carbon Dioxide
9Gas Exchange
9.1Gas Exchange System
10Infectious Diseases
10.1Infectious Diseases
10.2Antibiotics
11Immunity
12Energy & Respiration (A2 Only)
13Photosynthesis (A2 Only)
14Homeostasis (A2 Only)
14.1Homeostasis
14.2The Kidney
14.3Cell Signalling
14.4Blood Glucose Concentration
14.5Homeostasis in Plants
15Control & Coordination (A2 Only)
15.1Control & Coordination in Mammals
15.1.1Neurones
15.1.2Receptors
15.1.3Taste
15.1.4Reflexes
15.1.5Action Potentials
15.1.6Saltatory Conduction
15.1.7Synapses
15.1.8Cholinergic Synnapses
15.1.9Neuromuscular Junction
15.1.10Skeletal Muscle
15.1.11Sliding Filament Theory Contraction
15.1.12Sliding Filament Theory Contraction 2
15.1.13Menstruation
15.1.14Contraceptive Pill
15.2Control & Co-Ordination in Plants
16Inherited Change (A2 Only)
16.1Passage of Information to Offspring
16.2Genes & Phenotype
17Selection & Evolution (A2 Only)
17.2Natural & Artificial Selection
18Classification & Conservation (A2 Only)
18.1Biodiversity
18.2Classification
19Genetic Technology (A2 Only)
19.1Manipulating Genomes
19.2Genetic Technology Applied to Medicine
19.3Genetically Modified Organisms in Agriculture
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