Chapter 3.7 Mitosis
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- Created on: 14-06-17 11:24
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- 3.7 Mitosis
- Mitosis produces 2 daughter cells that have the same number of chromosomes as the parent cell
- Meiosis produces 4 daughter cells with half the number of chromosomes of the parent cell (mind map 9.2)
- Definition: a division of a cell that results in each of the daughter cells having an exact copy of the DNA of the parent cell.
- A mutation would cause the genetic make-up to be different
- INTERPHASE: a time when the cell is not dividing
- It is a period of considerable cell activity that includes the replication of DNA
- The 2 copies of DNA after replication remain joined at a place called the centromere
- It is a period of considerable cell activity that includes the replication of DNA
- The 4 stages of mitosis:
- 1. PROPHASE
- Chromosomes first become visible.
- They are initially long thin threads, but later shorten and thicken.
- In animal cells there are 2 cylindrical organelles called centrioles
- These centrioles move to opposite ends of the cells (known as poles)
- From each of the centrioles, spindle fibres develop which span from pole to pole
- The spindle fibres as a whole are called spindle apparatus
- A plant cell lacks centrioles, but they still have the spindle apparatus
- The nucleolus disappears and the nuclear envelope breaks down, leaving the chromosomes free in the cytoplasm
- These chromosomes are drawn towards the equator of the cell by the spindle fibres attached to the centromere of the chromosome
- The nucleolus disappears and the nuclear envelope breaks down, leaving the chromosomes free in the cytoplasm
- A plant cell lacks centrioles, but they still have the spindle apparatus
- The spindle fibres as a whole are called spindle apparatus
- From each of the centrioles, spindle fibres develop which span from pole to pole
- These centrioles move to opposite ends of the cells (known as poles)
- In animal cells there are 2 cylindrical organelles called centrioles
- They are initially long thin threads, but later shorten and thicken.
- Chromosomes first become visible.
- 2. METAPHASE
- Chromosomes are seen to be made up of two chromatids
- Each chromatid is an identical copy of DNA from the parent cell.
- Chromatids are joined by the centromere (mind map 8.2)
- It is to this centromere that some microtubules from the poles are attached.
- Also, the chromosomes are pulled along the spindle apparatus and arrange themselves across the equator of the cell.
- It is to this centromere that some microtubules from the poles are attached.
- Chromatids are joined by the centromere (mind map 8.2)
- Each chromatid is an identical copy of DNA from the parent cell.
- Chromosomes are seen to be made up of two chromatids
- 3. ANAPHASE
- Centromere divide into 2 and spindle fibres pull the individual chromatids making the chromosome apart.
- The chromatids move rapidly to their respective, opposite poles of the cell and now we refer to them as chromosomes
- WHAT IS THE DIFFERENCE BETWEEN A CHROMATID AND A CHROMOSOME
- A chromatid is one-half of two identical copies of a replicated chromosome.
- During cell division, the identical copies are joined together at the region of the chromosome called the centromere. They are known as sister chromatids
- the paired sister chromatids separate from one another in anaphase of mitosis,
- each is known as a daughter chromosome
- the paired sister chromatids separate from one another in anaphase of mitosis,
- During cell division, the identical copies are joined together at the region of the chromosome called the centromere. They are known as sister chromatids
- A chromatid is one-half of two identical copies of a replicated chromosome.
- The energy for the process is provided by the mitochondria, which gather around the spindle fibres
- WHAT IS THE DIFFERENCE BETWEEN A CHROMATID AND A CHROMOSOME
- The chromatids move rapidly to their respective, opposite poles of the cell and now we refer to them as chromosomes
- Centromere divide into 2 and spindle fibres pull the individual chromatids making the chromosome apart.
- 4. TELOPHASE AND CYTOKINESIS
- Chromosomes reach their respective poles and become longer and thinner, finally disappearing altogether
- Leaving only a widely spread chromatin
- The spindle fibres disintegrate and the nuclear envelope and nucleolus re-form
- Finally the cytoplasm divides in a process called cytokinesis
- DEFINITION: a chromatin is the material that makes up chromosomes. It consists of DNA and the protein histone
- The spindle fibres disintegrate and the nuclear envelope and nucleolus re-form
- Leaving only a widely spread chromatin
- Chromosomes reach their respective poles and become longer and thinner, finally disappearing altogether
- 1. PROPHASE
- Cell division in prokaryotic cells
- BINARY FISSION
- 1. The circular DNA molecule replicates and both copies attach to the cell membrane
- 2. Plasmids also replicate
- 3. The cell membrane begins to grow between the 2 DNA molecules and begins to pinch inward, dividing the cytoplasm into 2
- 4. A new cell wall forms between the two molecules of DNA, dividing the original cell into two identical daughter cells, each with a single copy of their circular DNA and a variable number of copies of plasmids
- 3. The cell membrane begins to grow between the 2 DNA molecules and begins to pinch inward, dividing the cytoplasm into 2
- 2. Plasmids also replicate
- 1. The circular DNA molecule replicates and both copies attach to the cell membrane
- BINARY FISSION
- Replication of viruses
- As viruses are non-living they cannot undergo cell division
- They replicate by attaching to their host cell with the attachm3ent proteins on their surface.
- They then inject their nucleic acid into the host cell
- The genetic info on the injected viral nucleic acid then provides the instructions for the host cells metabolic processes to start producing viral components which are then assembled into new viruses
- They then inject their nucleic acid into the host cell
- They replicate by attaching to their host cell with the attachm3ent proteins on their surface.
- As viruses are non-living they cannot undergo cell division
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