Mitosis

Question 1

What is mitosis?

Answer 1

The nuclear division which produces two genetically identical daughter nuclei each containing the same number of chromosomes as the parents nucleus.

Question 2

Where does mitosis occur?

Answer 2

In ALL the somatic cells (body cells)

Question 3

What is mitosis?

Answer 3

• Growth
• Cell replacement/regeneration
• Repair of tissues
• Asexual reproduction

Question 4

Where is the majority of the cell cycle?

Answer 4

Interphase (metabolic activity and growth)

Question 5

What happens in G1, the first growth phase?

Answer 5

Protein synthesis, cytoplasm and number of organelles increase rapidly, growth of cell

Question 6

What happens at S synthesis?

Answer 6

DNA replicated (DNA doubles), cells divide

Question 7

What happens in G2, second growth phase?

Answer 7

Proteins necessary for cell division are synthesised. Energy stores increased.

Question 8

What is interphase?

Answer 8

Period of growth and development. The cell grows and carries out normal cell activities, replicated all other organelles.

Question 9

Where does DNA replication occur?

Answer 9

During interphase

Question 10

What are the stages of mitosis?

Answer 10

Prophase
Metaphase
Anaphase
Telophase

Question 11

What happens at prophase?

Answer 11

• Chromatin condenses (shortened and thickens) to become visible as long threads called chromosomes.
• Each chromosome is made from two genetically identical chromatids held together by a centromere.
• Nuclear membrane disappears.
• Nucleolus disappears
• Centrioles move to the poles (opposite sides of the nucleus) and start to form spindles.

Question 12

What happens at metaphase?

Answer 12

• Chromosomes arrange at the equator of the spindle.
• Microtubules are attached to the centromeres at one end of the spindle and the centrioles at the other end.
• Microtubules of spindle attach to the centromere.

Question 13

What happens at anaphase?

Answer 13

• The centromere divides in two
• Spindle fibres contract and pull the chromatids apart to the opposite poles, centromere first.
• Chromatids are now called daughter chromosomes

Question 14

What happens at telophase?

Answer 14

• Daughter chromosomes reach the poles, they uncoil and lengthen to become chromatin.
• Nuclear membrane returns
• 2 new nuclei are formed
• Spindle fibres disintegrate

Question 15

What is cytokinesis?

Answer 15

It’s the division of the rest of the cell (cytoplasm and organelles) after the nucleus divides.
In animal cells the cytoplasm pinches in.
In plant cells a cell plate forms.

Question 16

What happens after mitosis and cytokinesis has been completed?

Answer 16

The cell will return to interphase where it continues to grow and perform regular cell activities.

Question 17

Use a flow diagram to show the cell cycle?

Answer 17

Interphase –> Mitosis (PMAT) –> Cytokinesis

Question 18

How do you calculate mitotic index?

Answer 18

number of cells in mitosis/ total n.o. visible cells in field of view x100

Question 19

What is cancer and what is it caused by?

Answer 19

It’s caused by uncontrollable mitosis. The cancerous cells divide repeatedly by mitosis forming a tumour (a regular mass of cells). Cancers are thought to be initiated by gene mutations in either oncogenes or tumour suppressor genes which controls cell divisions.