6.2 Mitosis

Question 1

What is mitosis

Answer 1

Division of the nucleus

Question 2

What is the purpose of mitosis

Answer 2

Ensures when a parent cell divides both daughter cells are identical

Question 3

What is initial the role of chromosomes in mitosis

Answer 3

Each chromosome is converted into two identical chromatids. These chromatids are then joined together in a region called the centromere.

Question 4

Why is it important to keep the two chromatids together

Answer 4

So that they can be precisely manoeuvred and segregated equally, one into each of the two new daughter cells

Question 5

What are the 4 stages of mitosis

Answer 5

Prophase, metaphase, anaphase and telophase

Question 6

How can you view each stage of mitosis

Answer 6

Using a light microscope

Question 7

What happens during prophase

Answer 7

• Chromatin fibres begin to coil and condense to from chromosomes
• The nucleolus disappears and the nuclear membrane begins to break down
• Protein microtubules form spindle shaped structures that link the poles of the cell
• The two centrioles migrate to opposite poles of the cell
• Spindle fibres attach to specific to specific areas on the centrometeres and start to move the chromosomes
  to the centre of the cell
• By the end of prophase the nuclear envelope has disappeared

Question 8

What is the role of the nucleolus

Answer 8

RNA synthesis

Question 9

What are chromatin fibres

Answer 9

Complexes made up of various protiens, RNA and DNA

Question 10

What is the role of the spindle fibres

Answer 10

To move the chromosomes into the correct positions before division

Question 11

What are centrioles

Answer 11

Cylindrical bundles of proteins that help in the formation of the spindle

Question 12

What happens during metaphase

Answer 12

Chromosomes are moved by the fibres to form a plane in the centre of the cell, caled the metaphase plate

Question 13

What happens during anaphase

Answer 13

The centrometres holding the pairs of chromatids together in each chromosome divide. Chromatids are separtated and pulled to opposite poles of the cell.

Question 14

What happens during telophase

Answer 14

The chromatids have reached the poles and are now called chromosomes. The two new sets of chromosomes assemble at each pole and the nuclear envelope reforms around them. Chromosomes begin to uncoil and the nucleolus is formed. Cytokinesis begins

Question 15

What is cytokinesis

Answer 15

The actual division of the cells into two separate cells. begins during Telophase

Question 16

How does cytokineses take place in animals

Answer 16

In animal cells the cleavage furrow forms around the middle of the cell. The cell surface membrane is then pulled inwards by the cytoskeleton until it’s close enough to fuse together, forming two cells

Question 17

How does cytokineses take place in plant cells

Answer 17

Vesicles from the golgi apparatus begin to assemble in the same place where the metaphase plate was formed. The vesicles fuse with each other and the cell surface membrane, dividing the cell into cell. New sections of the cell wall then form along the new sections of the cell membrane.

Question 18

Why does the dividing cell wall form after the daughter cells separate

Answer 18

Because if the cell wall formed before the cells split then they would immediately undergo osmotic lysis from the surrounding water