Mitosis is the cell division in which the nucleus divides into nuclei containing the same number of chromosomes. During mitosis, a parent cell reproduces to make to new daughter cells, each containing the same number of chromosomes. A major purpose for Mitosis is to reproduce cells for the growth and repair (to replace worn out or damage cells), for asexually reproducing organisms e.g. an Amoeba, mitosis is the way in which they reproduce offspring.
Mitosis has 6 phases which include:
Mitosis has 6 phases which include:
- Interphase
- Prophase
- Metaphase
- Anaphase
- Telophase
- Cytokinesis
GENERAL MITOSIS
INTERPHASE
The cell duplicates its DNA so that now the chromosomes in the nucleus each consist of two sister chromatids. Plant cell don’t usually have a centriole or centrosomes but are equipped with a microtubule organising centre
PROPHASE
Prophase is the phase in which certain cell structures begin to be broken down and others are built up, setting the right environment for the chromosomes to be divided. These changes include:
- The condensing of the chromosomes
- The forming of spindle fibres
- The disappearing of the nucleolus
METAPHASE
The chromosomes now align at the equator of the cell and the centromere of each chromosomes attaches to the microtubules. This is an important part of the division as if the chromosomes are not aligned correctly, the division will not occur properly so in order to avoid this, the cell will halt cell division and check for and fix any issues that may be there.
ANAPHASE
The COHESIN that is holding the sister chromatids together breaks down which enables them to separate from each other. The microtubules then pull the chromosomes to each end of the cell.
TELOPHASE
The cell is nearing the end of the cell division. The spindle fibres are broken down and two new nuclei begin to form, one being for each set of the chromosomes. As well as this, the nuclear membrane begins to reform and the nucleoli reappear. The chromosomes the return to their normal form.
CYTOKINESIS
This is a stage the somewhat overlaps with the other stages of mitosis. During cytokinesis the cytoplasm divides to create two new cells. By the end of cytokinesis you are left with two ne cells which are each equipped with their own set of chromosomes of which these chromosomes are identical to those of the “mother cell”.
MITOSIS: AMOEBAS
Binary fission is a type of mitosis that occurs in prokaryotic organisms such as protists. The process of mitosis is slightly different for these organisms. There are four stages of binary fission including:
- Replication
- Growth
- Segregation
- Division
REPLICATION
The amoeba copies its DNA at a location called the origin of replication. The amoeba does not have a nuclear membrane so the chromosome is found inside the nucleoid. The origin is the first part of the DNA to be replicated. Once replication has been completed each chromosomes forms a new circle of DNA and you are left with the two circles of DNA linked to each other.
GROWTH
The parent cell begins to enlarge quite a considerable amount and the DNA begins to unlink themselves. The two DNA copies begin to move away from each other to opposite poles of the cell.
SEGREGATION
The cell elongates itself in preparation for the division of the cell. The membrane pinches inward and a new cell wall called a septum begins to form in the middle of the cell which results in the two DNA copies being separated into two compartments.
DIVISION
The parent cell splits into two daughter cells as the septum separates down the middle. These two cells are released into their own individual lives at this point.