MITOSIS AND MEIOSIS TYPES OF CELL DIVISIONMITOSIS
WHAT IS MITOSIS?
Mitosis is a cell or nuclear division following the duplication of the chromosome, whereby each daughter cell or nucleus has exactly the same chromosomes content as as was in the parent cell. So in other words mitosis is the division of cell in which the daughter cell has the number of chromosomes as the parent cell.
Mitosis takes place in somatic cells. That is the body cells that are not involved in the production of gametes.
Mitosis takes place during an organism’s growth, development and asexual reproduction. In plants, mitosis takes place in the terminal bud of the shoot, at the tips of the shoots and roots.
Mitosis produces diploid cells. In other words, the number of chromosomes in each somatic cell of an organism is called the diploid number (2n)
STAGES OF MITOSIS
There are five stages of mitosis or phases of mitosis. These are
i. INTERPHASE OF MITOSIS: this is the latent or resting stage of the cell. At this stage, the cell has normal appearance of non-dividing cell condition. Chromosomes are too thread-like for clear visibility
ii. PROPHASE OF MITOSIS: the prophase is divided into two. They are late and early prophase. During early prophase the chromosomes become visible as they contract and nucleolus shrinks. Centroids are formed at the opposite sides of the nucleus. Spindles are formed during the late prophase, the chromosomes becomes shorter and fatter. Each is seen to contain or consist a pair of chromatids joined at the centromere and nucleus disappears. PROPHASE ENDS WITH THE BREAKDOWN OF NUCLEAR MEMBRANE
iii. METAPHASE OF MITOSIS: Metaphase also exists in early and late forms. During early metaphase of mitosis, the chromosomes arranged themselves on the equator of the spindle and at late metaphase, the chromatids draw apart at the centromere region.
iv. ANAPHASE OF MITOSIS: anaphase of mitosis also exist in early and late forms. During early anaphase, the chromatids part company and migrate to opposite poles of cells while in late anaphase, the chromosomes reach their destination.
v. TELOPHASE OF MITOSIS: Telophase is equally divided into early and late stages or forms. During the early Telophase, the cells starts to constrict across the middle. During late Telophase, the constrictions continues. The nuclear membrane and the nucleolus reforms in each daughter cell. Spindle apparatus generates. The chromosomes eventually regains their thread-like form and the cells returns to resting condition.
THE IMPORTANCE AND ROLES OF MITOSIS IN CELL DIVISION
The importance of mitosis can be seen in the following ways, they are
1. Mitosis helps in the repairs or replacement of damaged tissues
2. Mitosis promotes cell or growth in the cell
3. Mitosis serves as bases sexual or vegetative propagation In plants
4. Mitosis produces genetically identical offspring which are identical to the parents in all aspect
5. Mitosis helps to maintain the diploid number of the chromosome of the cell
EXAMPLES LIFE PROCESSES INVOLVED IN MITOSIS
An example of life processes of mitosis in animals includes the following
i. The processes of mitosis involves the formation of new cells in the Malphighian layer of the skin
ii. Life processes of mitosis involves the production of red blood cells and white blood cells in the bone marrow
iii. Life process in mitosis helps cell division in the liver
iv. Life processes of the mitosis helps in cell division in meristem or tips of roots
v. Life processes in mitosis helps in binary fission
vi. Life processes in mitosis helps in the growth of spermatogenesis
vii. Life processes in mitosis helps in the repair or healing of wound.
WHAT IS MEIOSIS AND TYPES OF MEIOSIS
Definition of meiosis
Meiosis is a two successive cell division with only one duplication the chromosome.
In meiosis, four daughters are formed. Meiosis is a reduction in cell division resulting in the reproduction of four daughters called haploid.
Meiosis takes place in reproductive cells, in ovules and pollen grains in plants, then ovaries and testes in animals.
In animals, meiosis occurs in the formation of gametes which is sex cells such as eggs and spermatozoa
THE PROCESS OF GAMETE FORMATION IS CALLED GAMETOGENESIS.
THE PROCESS INVOLVED IN THE PRODUCTION OF SPERMATOZOA IS CALLED SPERMATOGENESIS.
THE PROCESS INVOLVED IN THE PRODUCTION OF EGGS OR OVA BY THE OVARIES IS CALLED OOGENESIS
STAGES IN MEIOSIS
Meiosis consists of two successive division, they are
i. First meiotic division: this is very first stage when the parent cell divide into two
ii. Second Meiotic division: this second stage of meiosis is when the cells then divides itself again given a total of four daughter cells
Let’s look at the first stages of meiotic division.
THE FIRST MEIOSIS STAGE OF CELL DIVISION
The 1st stages of meiotic division in meiosis is divided into five stages and they are
1. INTERPHASE OF MEIOSIS: this is the resting stage of the cell. At this stage of meiosis, the chromosomes are not seen
2. PROPHASE 1: PROPHASE 1 OF MEIOSIS is divided into three stages and they are
i. Early prophase: at this stage in prophase of meiosis, the chromosomes contracts, becoming more clearly visible and the nucleus shrinks
ii. MID PROPHASE 1 OF MEIOSIS: in this stage of meiosis, the homologous chromosomes come together as synapsis forming a bivalent
iii. LATE PROPHASE 1 OF MEIOSIS: during this stage of prophase in meiosis, the chromosomes is seen to consist of a pair of chromatid at prophase 1, crossing over takes place. The points on the chromosomes where crossing over takes place are known as Chiasmata
3. METAPHASE 1 OF MEIOSIS: during metaphase 1 of meiosis, the nuclear membrane disappears and the spindle is formed. The bivalent chromosomes assembles at the equatorial region of the spindle
4. ANAPHASE 1 OF MEIOSIS: this stage of Anaphase in meiosis, the bivalent separates completely and each member chromosome moves to the opposite pole of the spindle
5. TELOPHASE 1 OF MEIOSIS: this stage in meiosis produces to daughter cells with chromosome number halved in the parent cells.
SECOND MEIOTIC DIVISION IN MEIOSIS
The second meiotic division in meiosis is made up of four stages and the division is similar to mitosis. At the end of the second division of meiosis, four groups of daughter cells are formed. The following are the stages outlined here for you
1. PROPHASE 11 OF MEIOTIC DIVISION IN MEIOSIS: IN prophase 11 of meiotic division, the two daughter cells prepares for the second meiotic division. This where the centrioles replicate and a new spindle is formed.
2. METAPHASE 11 OF MEIOTIC DIVISION IN MEIOSIS: Metaphase 11 of meiosis is where the chromosomes arrange themselves on the spindle in the usual way. Here the chromosomes appear doubled and the centromere starts to divide in the position of the equatorial plane,
3. ANAPHASE 11 OF MEIOTIC DIVISION IN MEIOSIS: in Anaphase 11 of meiotic division, each chromosome finally split into two. Where the actual chromosomal division takes place at Anaphase 11, each moves to the opposite poles of the cells
4. TELOPHASE 11 OF MEIOTIC DIVISION IN MEIOSIS: at this stage in meiotic division, the two cells are divided into four cells which are TETRAD. The four haploid cells are produced from the original diploid mother cell
IMPORTANCE OF MEIOSIS AND THE ROLES OF MEIOSIS
There are a lot of things to write about the importance of meiosis but I shall be limiting myself to the following
i. Meiosis aids the formation of male gametes or sperms in animals
ii. Meiosis aids in the formation of ova-eggs or female gametes in female animals
iii. Meiosis aids in the formation of pollen grains in anthers of flowering plants
iv. Meiosis also aids in the formation of ovules in ovaries of flowering plants
AREAS WHERE MEIOSIS OCCURS
1. Meiosis occurs in ovaries and anthers of plants
2. Meiosis occurs ovaries and testes of animals
DIFFERENCES BETWEEN MITOSIS AND MEIOSIS
There are a lot of differences but let us consider the major ones that feasible to deal with and they as follows
1. Mitosis takes place during growth of body or somatic cells
2. In mitosis, the number of chromosome in the parents and new cells are the same
3. In mitosis, two offspring are formed
4. In mitosis, there is no exchange of materials between variation; the chromatids
5. In mitosis, chromosomes are arranged in pairs in both parents and new cells
6. There is no formation of bivalent in mitosis
7. There is no crossing over in mitosis
8. Mitosis involves only one stage of division
1. Meiosis takes place only in the production of gametes
2. In meiosis, the number of chromosomes in the new cell is half the number in the parent cells
3. In meiosis, four offspring are formed
4. In meiosis, chromosomes are arranged in pairs in the parent cell but new cells have only one of the homologous pair
5. In meiosis, there is exchange in materials
6. In meiosis, the whole chromosomes form bivalent
7. In meiosis, there is crossing over
8. Meiosis involves two stages of division
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