3. Mitosis

Question 1

What is Mitosis?

Answer 1

Mitosis produces cells that are genetically the same as the parent cell, it is the basis of asexual reprodution. It plays an important part in the development of embryos, the growth and development of our bodies. as well as replacing old or damaged cells for repair.

1. Allows genetic information (DNA) to be transmitted from one generation to the next
2. Allows new cells in multicellular organisms to replace dead or damaged cells (mitosis)
3. Provides a way for multicellular organisms to grow following fertilisation
4. Allows unicellular organisms to reproduce

Question 2

Draw the Cell Cycle

Answer 2

Question 3

Interphase (Late G2 Phase)

Answer 3

Has already replicated its DNA, so the chromosomes in the nucleus each consist of two connected copies, called sister chromatids. DNA is uncoiled during the majority of the cell cycle, making the DNA available to the proteins involved in DNA replication and transcription.

Question 4

Prophase

Answer 4

• The chromosomes start to condense
• The mitotic spindle begins to form. (strong fibers part of the cytoskeleton)
• The nucleolus, where ribosomes are made, disappears. As the nuclear membrane begins to break down to release chromosomes.
• The mitotic spindle grows more, and some of the microtubules start to “capture” chromosomes.

Question 5

Metaphase

Answer 5

In metaphase, the spindle has captured all the chromosomes lined up along the equator of the cell.
All the chromosomes align at the metaphase plate (not a physical structure, just a term for the plane where the chromosomes line up)

Before proceeding to anaphase, the cell will check to make sure that all the chromosomes are correctly attached to microtubules. Ensures that the sister chromatids will split evenly. If a chromosome is not properly aligned, the cell will halt division until the problem is fixed.

Question 6

Anaphase

Answer 6

In anaphase, the sister chromatids separate from each other and are pulled towards opposite ends of the cell as spindle fibres shorten.
Sister chromatids separate, each chromatid now its own chromosome.
Microtubules not attached to chromosomes elongate and push apart, separating the poles and making the cell longer.

Question 7

Telophase

Answer 7

• Two identical daughter cells are ready to divide, and begin to re-establish normal structures as cytokinesis (division of the cell contents) takes place.
• The mitotic spindle is broken down into its building blocks.
• Two new nuclei form, one for each set of chromosomes. Nuclear membranes and nucleoli reappear.
• Chromosomes uncondense

Question 8

Cytokinesis

Answer 8

Division of the cytoplasm to form two new cells.
In animal cells, cytokinesis is contractile, the cell is pinched in the middle by a band of filaments made of a protein (actin) to separate into two cells.

The cell wall of plant cells means that a structure called the cell plate must form down the middle of the cell, splitting it into two daughter cells separated by a new wall.