is a nuclear division giving rise to genetically identical cells in which the chromosome number is maintained by the exact duplication of chromosome.
Stages of Mitosis #
Prophase
- Formation of spindle.
- It is the longest phase.
- Chromosomes shorten and thicken by coiling.
- Chromosomes now available as a double structure.
- In animal cells centrioles move to opposite poles.
- A star from short microtubules radiating from centrioles.
- The spindle is formed.
- Chromatids form chromosomes.
- Nuclear envelope disappear
Metaphase
- Chromosomes line up at the equator of the spindle attached by the centromeres to the spindle.
- Chromosomes move to metaphase plate
Anaphase
- A very rapid stage.
- The centromers split into two and the spindle pull the daughter chromosomes to opposite poles.
- The separated are pulled behind the centromeres.
- The shortening of the spindle fiber by the removal of the subunits account to moving of chromatids during anaphase
Telophase
- The chromatids reach the opposite poles.
- They uncoil and lengthen to from chromatin again.
- The spindle fiber disintegrate and centrioles replicate.
- Nuclear envelope reforms
Cytokinesis
Is the actual division of the cytoplasm to form two daughter cells
- In animal cells a ring of actin filaments forms round the equator of the cell, and then tightens to form a cleavage furrow, which splits the cell in two
- In plant cells vesicles move to the equator, line up and fuse to form two membranes called the cell plate.
Explain the significance of mitosis[8] #
- genetic stability: Mitosis produces two cells with the same chromosomal number as the mother cell.
- growth: the number of cells in organism increase with mitosis.
- cell replacement: Replacement of cell tissue involve mitosis.
- regeneration: Some animals are also regenerated some parts of their body by mitosis.
- asexual reproduction: Mitosis is the basic of asexual reproduction of new individuals of a spice by one parent organism.
Outline the differences between mitosis and meiosis[8] #
| mitosis | meiosis | |
|---|---|---|
| Prophase | homologous chromosomes remain separate | homologous pair up; |
| no formation of chiasmata; | chiasmata; | |
| metaphase | pairs of chromatids line up on spindle equator | pairs of chromosomes line up on spindle equator |
| Anaphase | centriomeres divide | centromeres don’t divide; |
| chromatids separate | chromosomes separate; | |
| chromatids identical | chomatids may not be identical | |
| telophase | sane no. chromosomes in daughteer as i parent | half no. of chromosomes in daughter cells |
| may occur in haploid, diploid cells | only occurs in diploid cells |
What is the name given to the division of the cytoplasm at the end of mitosis? How is this process different in plant and animal cells?
