Mitosis

What is the overall role of mitosis

To produce 2 daughter cells, which are genetically identical to each other and to the parent cell.

What is mitosis important for

Growth, repair of tissues, cell replacement, and asexual reproduction

Growth

Genetically identical cells have the same cell structure and can fulfill the same function as the parent cell.

Repair of tissues

Damaged cells can be replaced by genetically identical cells that can carry out the same function.

Cell replacement

Some cells have a limited life span, such as erythrocytes, and must be regularly replaced with new cells of the same type.

Asexual reproduction

Some eukaryotic organisms can reproduce using mitosis to give genetically identical offspring (clones).

What are the phases of mitosis

Prophase, metaphase, anaphase and telophase

Prophase

Chromosomes condense and become visible as two chromatids joined at centromere. Centrioles move to opposites poles and form a spindle of microtubules. The nuclear envelope disintegrates and the chromosomes move towards the equator.

Metaphase

Chromosomes line up at the equator of the cell. Some microtubules span the cell while others attach to the centromeres of the chromosomes via the kinetochore.

Anaphase

Centromeres split, separating the chromatids. Daughter chromosomes are pulled, centromere first, towards opposite poles of the cell by the shortening spindle fibres.

Telophase

Chromosomes uncoil and become indistinct as the nuclear envelope reforms. Cytokinesis may start.

Why must chromosomes condense at the beginning of mitosis

So that they can be easily moved around the cell by the mitotic spindle to ensure each daughter cell receives the correct number of chromosomes.

Why don’t chromosomes condense earlier before mitosis

Because when they are compacted their normal activities e.g. transcription, cannot take place.

In which tissues does mitosis occur in plants

Meristem

Where is meristem located in plants

The tips of roots and shoots and the cambium.

Where does mitosis occur in animals

In most tissues

What occurs to the shape of an animal cell in mitosis

Becomes rounded

What occurs to the shape of an plant cell in mitosis

does not change due to cell wall

What occurs to the spindles after mitosis in animal cells

Disappear before cytokinesis

What occurs to the spindles after mitosis in plant cells

Partly remain during cytokinesis.

Role of microfilaments in animal cells during mitosis

Constrict cell to form cleavage furrow

How does cytokinesis occur in animal cells

Via a cleavage furrow

How does cytokinesis occur in plants

Via a cell plate