Mitosis & Cell cycle

Question 1

What does the Cell Theory state?

Answer 1

The cell is a fundamental unit of structure, function & organisation in all living organisms. All new cells are formed from other existing cells.

Question 2

The different stages of the cell cycle?

Answer 2

G1, S, G2, followed by mitosis and cytokinesis (M phase)

Question 3

What happens in the G1 Phase?

Answer 3

Cell synthesis organelles such as mitochondria and ribosomes, cell builds up a large store of energy. Proteins such as histones, ribosomal proteins and tubulin (for the making of spindle fibres) and also manufactured.

Question 4

What happens in the S phase?

Answer 4

DNA replication occurs. The centrosome is also duplicated.

Question 5

Define mitosis

Answer 5

The nuclear division of a cell to form 2 genetically identical daughter cells

Question 6

What are centrosomes?

Answer 6

Non-membranous organelles found only in animal cells.
Function: Microtubule organizing center

Question 7

What are the 4 stages of mitosis?

Answer 7

Prophase, Metaphase, Anaphase, Telophase (PMAT)

Question 8

Describe what occurs during prophase.

Answer 8

• Condensation of chromatin into chromosomes.
• (In animal cells) Centrosomes move to opposite ends of the cell
• Nuclear envelope disintegrates
• Formation of spindle fibre
• Kinetochore assembles at the centromere of the chromosome

Question 9

Describe what occurs during metaphase.

Answer 9

• Alignment of chromosomes on the equator/metaphase plate
• Spindle fibres attached to chromosomes

Question 10

Describe what occurs during Anaphase.

Answer 10

• Centromere of each chromosome divides, causing the two sister chromatids of each chromosome to separate
• Each chromatid is now called an individual chromosome
• Chromosomes move (centromere first) to the opposite poles of the spindle, because of the shortening of their kinetochore microtubules (spindle fibre)

Question 11

Describe what occurs during Telophase.

Answer 11

• Chromosomes reach their respective poles.
• Chromosomes uncoil and return to chromatin form.
• Spindle fibres disintegrate
• Nuclear envelope reforms.

Question 12

Describe the process of cytokinesis IN ANIMALS.

Answer 12

A cleavage furrow develops in the cell membrane. The cell membranes in the furrows eventually join up and completely separate the two daughter nuclei.

Question 13

Describe the process of cytokinesis IN PLANTS

Answer 13

A series of lined up Golgi vesicles fuse to form the cell plate, which extends outwards across the equator of the parent cell.
Cell plate eventually fuses with the parent cell wall and cell membrane, separating the two daughter cells

Question 14

What are cell cycle checkpoints?

Answer 14

A control point where the stop and go-ahead signals regulate the cycle. A cell is only allowed to proceed to the next phase of the cell cycle if it has properly completed the previous phase.
Checkpoints monitor: DNA replication, DNA damage & chromosome-to-spindle attachments.

Question 15

Significance of Mitosis

Answer 15

• Two daughter nuclei formed are genetically identical
• Maintains the genetic stability of an organism in the growth (of a multicellular organism), the repair of worn-out parts the body, asexual reproduction