Cell Division: Stages of Mitosis | A-level Biology | OCR, AQA, Edexcel
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Cell Division: Stages of Mitosis
Cell Division: Stages of Mitosis in a Snap! Unlock the full A-level Biology course at http://bit.ly/2uJl0RB created by Adam Tildesley, Biology expert at SnapRevise and graduate of Cambridge University.
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The key points covered of this video include:
1. Chromosomes in Interphase
2. Overview of Mitotic Stages
3. Prophase
4. Metaphase
5. Anaphase
6. Telophase
7. Cytokinesis
8. Comparing Animal and Plant Mitosis
Chromosomes in Interphase
In interphase the DNA is replicated. Before replication each chromosome exists as a single chromatid. After replication each chromosome is made up of two sister chromatids - joined by a centromere.
Overview of Mitotic Stages
Mitosis is made up of four main stages: prophase, metaphase, anaphase, and telophase. The overall process of mitosis involves the separation of chromosomes to opposite parts of the cell so that the cell can divide.
Prophase
Prophase is the first stage in mitosis and is the first stage where we can see individual chromosomes. Before prophase DNA is in long tangled threads - during prophase it supercoils into a shorter, more condensed structure. The nuclear envelope holding the DNA disintegrates and breaks down. The centrioles (organelles made of protein) divide and move to the opposite ends of the cell (the poles). The spindle fibres (long fibres of protein) form from the centrioles and make up the spindle apparatus. Plant cells don't have centrioles - but they do have a spindle apparatus that forms straight from the cytoplasm. Summary of Prophase.
Metaphase
Metaphase is the second phase of mitosis and involves the chromosomes lining up at the centre of the cell. The chromosomes become attached to spindle fibres at their centromere. The chromosomes are then pulled along the spindle fibres to the equator of the cell. This prepares the chromatids in each chromosome ready for separation in anaphase. Summary of Metaphase.
Anaphase
In anaphase the chromatids on each chromosome are separated and pulled to opposite poles of the cell. The chromosomes split and while still attached to the spindle fibres move to the poles with the help of motor proteins. This process requires ATP so the mitochondria gather around the spindle fibres to provide it. The spindle fibres are vital to anaphase - they are positioned to guide chromatids to the poles. Once the chromatids reach the opposite poles of the cell we refer to them as chromosomes. Anaphase results in each pole getting a full set of chromosomes which are identical to the chromosomes on the other pole. Summary of Anaphase.
Telophase
At the end of telophase the nucleus reappears and the chromosomes become invisible under the microscope. Once the separated chromatids reach the poles the spindle fibres begin to disintegrate. The chromosomes now begin to lengthen and uncurl meaning they can't be seen under the microscope. The nuclear envelope starts to reform around the lengthening chromosomes. Because there are two sets of chromosomes, at the end of telophase the cell ends up with two distinct nuclei. The cell is now ready for the cytoplasm to split in cytokinesis to make two cells. Summary of Telophase.
Cytokinesis
After telophase the cell is split to create two new daughter cells with identical nuclei. In animals the plasma membrane folds inwards until the two dents meet to separate the two daughter cells. In plant cells cellulose starts to build up at the equator - we call this the end plate. Plasma membrane forms in the middle of the end plate resulting in two fully separated plant cells.
Summary
In prophase the DNA supercoils and nuclear envelope disintegrates
The centrioles divide and form spindle fibres
In metaphase the chromosomes line up at the equator
In anaphase the chromatids separate
In telophase the nucleus reforms
In animals cytokinesis involves infolding of the membrane
In plants the new cell wall and plasma membrane form at the end plate
SnapRevise is the UK’s leading A-level and GCSE revision & exam preparation resource offering comprehensive video courses created by A* Oxbridge tutors. Our courses are designed around the OCR, AQA, SNAB, Edexcel B, WJEC, CIE and IAL exam boards, concisely covering all the important concepts required by each specification. In addition to all the content videos, our courses include hundreds of exam question videos, where we show you how to tackle questions and walk you through step by step how to score full marks.
Sign up today and together, let’s make A-level Biology a walk in the park!
The key points covered of this video include:
1. Chromosomes in Interphase
2. Overview of Mitotic Stages
3. Prophase
4. Metaphase
5. Anaphase
6. Telophase
7. Cytokinesis
8. Comparing Animal and Plant Mitosis
Chromosomes in Interphase
In interphase the DNA is replicated. Before replication each chromosome exists as a single chromatid. After replication each chromosome is made up of two sister chromatids - joined by a centromere.
Overview of Mitotic Stages
Mitosis is made up of four main stages: prophase, metaphase, anaphase, and telophase. The overall process of mitosis involves the separation of chromosomes to opposite parts of the cell so that the cell can divide.
Prophase
Prophase is the first stage in mitosis and is the first stage where we can see individual chromosomes. Before prophase DNA is in long tangled threads - during prophase it supercoils into a shorter, more condensed structure. The nuclear envelope holding the DNA disintegrates and breaks down. The centrioles (organelles made of protein) divide and move to the opposite ends of the cell (the poles). The spindle fibres (long fibres of protein) form from the centrioles and make up the spindle apparatus. Plant cells don't have centrioles - but they do have a spindle apparatus that forms straight from the cytoplasm. Summary of Prophase.
Metaphase
Metaphase is the second phase of mitosis and involves the chromosomes lining up at the centre of the cell. The chromosomes become attached to spindle fibres at their centromere. The chromosomes are then pulled along the spindle fibres to the equator of the cell. This prepares the chromatids in each chromosome ready for separation in anaphase. Summary of Metaphase.
Anaphase
In anaphase the chromatids on each chromosome are separated and pulled to opposite poles of the cell. The chromosomes split and while still attached to the spindle fibres move to the poles with the help of motor proteins. This process requires ATP so the mitochondria gather around the spindle fibres to provide it. The spindle fibres are vital to anaphase - they are positioned to guide chromatids to the poles. Once the chromatids reach the opposite poles of the cell we refer to them as chromosomes. Anaphase results in each pole getting a full set of chromosomes which are identical to the chromosomes on the other pole. Summary of Anaphase.
Telophase
At the end of telophase the nucleus reappears and the chromosomes become invisible under the microscope. Once the separated chromatids reach the poles the spindle fibres begin to disintegrate. The chromosomes now begin to lengthen and uncurl meaning they can't be seen under the microscope. The nuclear envelope starts to reform around the lengthening chromosomes. Because there are two sets of chromosomes, at the end of telophase the cell ends up with two distinct nuclei. The cell is now ready for the cytoplasm to split in cytokinesis to make two cells. Summary of Telophase.
Cytokinesis
After telophase the cell is split to create two new daughter cells with identical nuclei. In animals the plasma membrane folds inwards until the two dents meet to separate the two daughter cells. In plant cells cellulose starts to build up at the equator - we call this the end plate. Plasma membrane forms in the middle of the end plate resulting in two fully separated plant cells.
Summary
In prophase the DNA supercoils and nuclear envelope disintegrates
The centrioles divide and form spindle fibres
In metaphase the chromosomes line up at the equator
In anaphase the chromatids separate
In telophase the nucleus reforms
In animals cytokinesis involves infolding of the membrane
In plants the new cell wall and plasma membrane form at the end plate
5 سال پیش
در تاریخ 1398/01/29 منتشر شده
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