3.7 mitosis

Question 1

What is mitosis?

Answer 1

The division of a cell that results in each of the daughter cells having an exact copy of the DNA of the parent cell.

Question 2

What is interphase?

Answer 2

• the period before mitosis before the cell starts to divide.
• involves the replication of DNA
• the two copies of DNA remain connected by the centromere

Question 3

What are the stages of mitosis?

Answer 3

(interphase)
prophase
metaphase
anaphase
telophase
(cytokinesis)

Question 4

What happens during prophase?

Answer 4

• chromosomes first become visible
• centrioles move to opposite poles of the cell
• spindle fibres develop from the centrioles
• the nucleolus disappears and the nuclear envelope breaks down, leaving the chromosomes free in the cytoplasm
• chromosomes are drawn towards the equator by the spindle fibres

Question 5

What happens during metaphase?

Answer 5

• chromosomes are seen to be made up of two chromatids, each with an identical copy of DNA
• chromatids are joined to a centraomere
• chromosomes are pulled along the spindle apparatus and arrange themselves along the equator.

Question 6

What happens during anaphase?

Answer 6

• centromeres divide into two and the spindle fibres pull the chromatids apart.
• chromosomes move rapidly to opposite poles
• the energy for this is provided by the mitochondria.

Question 7

What happens during telophase and cytokinesis?

Answer 7

• chromosomes reach their poles and become longer and thinner, eventually disappearing leaving only chromatin
• spindle fibres disintagrate
• nuclear envelope and nucleolus re-form
• cytoplasm divides in cytokinesis.

Question 8

How do prokaryotic cells divide?

Answer 8

By binary fission.

Question 9

Describe the process of binary fission.

Answer 9

1) Circular DNA molecule replicates and attaches to cell membrane
2) plasmids also repicate
3) Cell membrane begins to grow between the 2 DNA molecules and pinches inward, dividing the cytoplasm into two.
4) A new cell wall forms between the two molecules of DNA, dividing the cell into 2 daughter cells.

Question 10

Describe the replication of a virus.

Answer 10

1) attach to host cell with the attachment proteins on their surface.
2) inject nucleic acid into host cell
3) nucleic acid provides instructions for the host cell to make viral components, nucleic acid, enzymes and structural proteins which are then assembled into new viruses.