3.2.2 All cells arise from other cells

Question 1

Give the processes which occur during interphase. (4 marks)

Answer 1

• DNA replication
• Protein synthesis
• Increase in the number of organelles
• increase in the volume of cell

Question 2

what stage does DNA replicate in?

Answer 2

S phase

Question 3

what is the importance of mitosis? (4 marks)

Answer 3

• genetically identical cells
• increase cell number
• asexual reproduction
• to replace cells

Question 4

why were the cells on the slide stained?

Answer 4

to make chromosomes visible

Question 5

If the DNA of a cell is damaged, a protein called p53 stops the cell cycle

Mutation in the p53 gene could develop cancer. Explain how. (3 marks)

Answer 5

1. cancer cells have damaged DNA
2. p53 is not made
3. cell with faulty DNA completes cell cycle
4. uncontrolled division leads to cancer

Question 6

describe what happens in anaphase (2 marks)

Answer 6

The spindle fibres contract
This causes the centromeres divide
This separates the sister chromatids
pulls them to opposite poles of the cell

Question 7

describe what happens in prophase?

Answer 7

chromosome becomes visible
chromosomes condense and become thicker
nuclear envelope disintegrates

Question 8

describe what happens in metaphase?

Answer 8

• chromosomes align on the equator of the cell
• spindle fibres attach to the chromosomes by their centromeres.

Question 9

describe what happens in telophase?

Answer 9

• the nuclear envelope reforms
• spindle fibres break down
  -chromosomes uncoil an become longer and thinnre

Question 10

what occurs in cytokinesis

Answer 10

• cytoplasm divides
• producing 2 new cells

Question 11

what are the cells like in mitosis

Answer 11

gentically identtical

Question 12

why does the mass of DNA increase?

Answer 12

cause DNA is replicating

Question 13

describe the apperance of chromosomes in prophase?

Answer 13

the chromosomes become visible
they condense and
are short and thick

Question 14

describe the apperance of chromosomes in metaphas?

Answer 14

the chromosomes appear as two sister chromatids joined at the centromere

Question 15

describe the appearance of chromosomes in anaphase?

Answer 15

centromeres have divided
sister chromatids are separated to opposite pole of the cell

Question 16

describe the apperance of chromosomes in telophase

Answer 16

• chromosomes beome longer and thin

Question 17

what is the process in which bacteria able to replicate

Answer 17

binary fission

Question 18

Descrribe binary fission in bacteria

Answer 18

plasmids and cirular DNA replicate
the move to opposite poles of cell
cytoplasm divides

Question 19

do viruses undergo cell division

Answer 19

no

Question 20

what is cancer

Answer 20

uncontrolled and rapid cell divison

Question 21

Explain why you have to push down hard on the cover slip, but do not push the cover slip sideways. (2 marks)

Answer 21

push hard- to spread the tissue
dont push sideways- to avoid cells rolling together/ breaking chromosomes

Question 22

explain why you have to push hard on the cover slip

Answer 22

to spread the tissue to one layer of cells thick and allows light to travel through

Question 23

explain why you shouldnt push sideways on the cover slip?

Answer 23

to prevent chromosomes from breaking

Question 24

Describe the role of the spindle during mitosis. (2 marks)

Answer 24

-they attach to chromosomes by their centromeres
- they cause the sister chromatids to separate and pull them to opposite poles

Question 25

explain why the root tip was used to investigate the stages of mitosis (1 mark)

Answer 25

the site of mitosis in the meristem tissue

Question 26

explain why a stain was used (1 mark)

Answer 26

to distinguish the chromosomes

Question 27

explain why the root tip was firmly squashed. (1 mark)

Answer 27

A thin layer which allows light to travel through

Question 28

Explain one advantage of cells lining in the human gut dividing very frequently. (1 mark)

Answer 28

damaged cells are replaced quicker

Question 29

Describe the role of the centromere in mitosis. (2 marks)

Answer 29

- they hold chromatids together - spindle fibres attach to centromeres - allows chromatids to separate to move to opposite poles

Question 30

Why is mitosis important in the life of an organism. (2 marks)

Answer 30

- asexual reproduction - to replace cells - increase cell number

Question 31

what is the purpose of treatments to treat cancer cells

Answer 31

they disrupt spindle activity

Question 32

what happens when spindle fibre formation is stoppedd?

Answer 32

no anaphase spindle fibres are unable to attach to chromsomes via their centromeres sister chromatids arent pulled to opposite poles prevents DNA replication

Question 33

what is the equation for mitotic index?

Answer 33

number of ccells undergoing mitosis / total number of cells