[Unit 3.7] | Mitosis

Question 1

Define Mitosis.

Answer 1

A form of cell division that produces 2 daughter cells with identical genetic material.

Question 2

Name the 5 stages of mitosis.

Answer 2

Prophase
Metaphase
Anaphase
Telophase
Cytokinesis

“PMATC”

Question 3

Describe Prophase.

Answer 3

[Shortcut: Chromosomes condensing, Spindle forming, Nucleus breaking down]

• The chromosomes condense (shorten & thicken) and become visible.

• The 2 centrioles move to opposite ends of the cell and spindle fibres develop across them to form the spindle apparatus.

• The nucleolus disappears and the nuclear envelope disappears.

Question 4

Describe Metaphase.

Answer 4

[Shortcut: Centromeres, Alignment]

• (The chromosomes are seen to be made up of a centromere and 2 chromatids.)

• Microtubles from the poles attach to the centromeres and pull the chromosomes along the spindle apparatus so they align along the equator of the cell.

Question 5

Describe Anaphase.

Answer 5

[Shortcut: Chromatids separated on either pole, Becoming Chromosomes]

• The centromeres split and the spindle fibres pull the chromatids to either pole of the cell.

• The separated chromatids are now referred to as chromosomes.

• (Energy for this process is provided by mitochondria gathered nearby the spindle fibres)

Question 6

Describe Telophase.

Answer 6

[Shortcut: Chromosomes disappear, Spindle disintegrates, Nucleus re-forms]

• The chromosomes become longer and thinner and are no longer visible.

• The spindle apparatus disintegrates.

• The nucleolus and nuclear envelope re-form.

Question 7

Describe Cytokinesis.

Answer 7

The cytoplasm divides to form 2 genetically identical daughter cells.

Question 8

Describe the process of Binary Fission (Prokaryotic Cell Division).

Answer 8

• Circular DNA is replicated and both copies attach to the membrane.

• The plasmids replicate.

• The cell membrane elongates and pinches inwards.

• A new cell wall forms and divides the 2 daughter cells, each woth one copy of circular DNA and a variable number of plasmids.

Question 9

Explain how viruses replicate.

Answer 9

• They attach to a host cell via their attachment proteind.

• They inject their nucleic acids into the host cell, which contain “instructions” to produce viral components, nucleic acid, enzymes and structural proteins

• The produced components are then assembled to make new viruses.