Amphibian oocytes can remain for years in the diplotene stage of meiotic prophase. This state resembles the G₂ phase of the cell division cycle (see Chapter 8). Resumption of meiosis in the amphibian primary oocyte requires progesterone.

Cells usually stop dividing after certain number of divisions. In malignant or cancerous cells this automatic stoppage of cell division does not work. As a result ma+gnant cells keep on dividing endlessly causing the cancerous growth

It is a type of cell division in which a single cell divides in order to produce two genetically identical “daughter cells”. The purpose of mitosis is: Mitosis is required for growth, repair, and asexual reproduction.

The cell cycle culminates in the division of the cytoplasm by cytokinesis.

We know that, Roots cells are diploid in nature therefore chromosome number of root cell as per the question will be 24 chromosomes.

The complex formed by a pair of synapsed homologous chromosomes is called a bivalent or a tetrad. It consists of four chromatids.

Kinetochores are disc-shaped structures on chromosomes, which help in the attachment of spindle fibres.

Syncytium is the term given to multinucleated condition of the cell.

On the beginning of diplotene stage, synaptonemal complex dissolutes and recombined homologous chromosomes separate from each other.

Interphase is the period between the two successive mitotic cell divisions.

Colchicine is a mitotic inhibitor, so it inhibits the M phase or mitotic phase.

Two phases of meiotic division: 
(i) Meiotic cell division is divided into two phases Meiosis I and Meiosis II. 
(ii) In the meiotic I division, the homologous chromosomes pair to form bivalents. Exchange of genetic material takes place. 
(iii) The chromosomes now separate and get distributed into daughter cells. 
(iv) Prophase I is divided into five sub-stages : Leptotene, Zygotene, Pachytene, Diplotene and Diakinesis. 
(v) During Metaphase I, the bivalents get arranged on equatorial plate with their arms on the plate but the centromere is directed towards opposite pole. It is followed by Anaphase I.



Fig. Stages of meiosis
(vi) Now the homologous chromosomes repel each other, and move to the opposite poles with both their chromatids. 
(vii) In this way each pole gets half the chromosomes number of the parent cell. 
(viii) In telophase I, the nuclear envelope and nucleolus again appear. Meiosis II is quite similar to mitosis. 
(ix) The centromere of each chromosome breaks, separating the chromatids, one each to a daughter cell.
(x) The meiotic cell division maintains the chromosome number of a species. 
(xi) As a result of meiotic division, the four daughter cells are formed with half the chromosome number (haploid) in each cell.

Difference between Mitosis and Meiosis

(i) Stages and type of cell division are (A) Metaphase -I-meiosis(B) Anaphase-I-meiosis
(ii) For metaphase-I : It is the stage followed by prophase (same as mitosis).
Following changes are observed during this stage
(i) The bivalents during this phase arrange themselves on the two parallel equatorial plates.
(ii) The centromeres project little bit towards periphery.Since, there are two centromeres in each bivalent.Thus, each centromere is joined by chromosomal fibres.
(iii) The fibres of the homologous chromosomes are always in the opposite directions.

Centrioles play an important role in formation of spindle during call division. They organise the mitotic spindle and thus, help in the completion of cytokinesis. They generate the cell's cytoskeleton and help in the formation of the mitotic spindles. In organisms with flagella and cilia, the position of these organelles is determined by the mother centriole, which becomes the basal body.

cell division, cell reproduction or cell multiplication is the process of formation of new daughter cells from the pre-existing cell or parent cell.
It is three types
(i) Amitosis
(ii) Mitosis
(iii) Meiosis.
A cell divides when it attains the size and the nucleocytoplasmic ratio disturbs. The DNA duplication also causes a cell to divide.