Question

what is the stages of mitosis????​

Answer 1

These stages are prophase,prometaphase, metaphase, anaphase, and telophase. During mitosis, the chromosomes, which have already duplicated, condense and attach to spindle fibers that pull one copy of each chromosome to opposite sides of the cell.

Answer 2

Stages of Mitosis:

Prophase:  

 The first stage of mitosis.

 Chromosomal material undergoes condensation.

 Chromosomes each with 2 sister chromatids attached together at centromere, are formed.

 Duplicated centrioles begin to move towards opposite poles in animal cells.

 Nucleolus, nuclear membrane, endoplasmic reticulum and Golgi complex disappear.

 Initiation of assembly of mitotic spindle and microtubules occurs.

Spindle fibres:  

 Are system of microtubules radiating from centriole.

 Are made of tubulin proteins.

 Are attached to centromeres of chromosomes.

 Responsible for directed movement of chromosomes during cell division.

Metaphase:  

 Complete disintegration of nuclear membrane marks start of metaphase; hence chromosomes are spread through the cytoplasm.

 Condensation of chromosomes is completed, thus they can be observed clearly under the microscope.

 Metaphase is the stage at which morphology of chromosomes is most easily studied.

 Metaphase chromosome is made of two sister chromatids which are held together at centromere.

Kinetochores:

 Are small, disc shaped structures that serve as sites for attachment of spindle fibres.

 Spindle fibres arrange chromosome at equatorial plane called metaphase plate.

Characteristics of metaphase:

 Chromosomes lie at equator with one chromatid of each chromosome connected by its kinetochore to spindle fibres from one pole and sister chromatid connected by its kinetochore to spindle fibres the opposite pole.

 Plane of alignment of chromosomes at metaphase is referred to as metaphase plate.

Key features of metaphase:

 Spindle fibres attach to kinetochore of chromosomes.

 Chromosomes are aligned along metaphase plate at equator.

Anaphase:  

 Shortest stage of mitosis.

 Each chromosome arranged at metaphase plate is split and the two daughter chromatids begin to migrate towards the opposite poles.

 The centromere of each chromosome is towards the pole while the arms of chromosome trail behind.

Key features of anaphase:

• Centromeres split and chromatids separate.

• Chromatids move to opposite poles.

Telophase:

 Chromosomes reach opposite poles, lose their individuality and decondense.

 Nuclear envelop reappears around chromatin material.

 Nucleoli, Endoplasmic reticulum, Golgi complex reappear.

Cytokinesis: Division of cytoplasm and cell organelles that results in formation of two daughter cells.

 Cell furrow method: A furrow appears in the plasma membrane which gradually deepens and ultimately joins in the centre diving cell cytoplasm into two.

Cell Plate Method:

 Cytokinesis cannot occur by cell furrow method in plant cells because they have a rigid cell wall.

 In plant cells, wall formation starts in the centre of cell and grows outward to meet the lateral walls.

 Cell plate is precursor of cell wall representing middle lamella between walls of adjacent cells.

 At the time of cytoplasmic division, organelles like mitochondria and plastids get distributed between the two daughter cells.

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