3.2.2 All cells arise from other cells Flashcards
Give the processes which occur during interphase. (4 marks)
- DNA replication
- Protein synthesis
- Increase in the number of organelles
- increase in the volume of cell
what stage does DNA replicate in?
S phase
what is the importance of mitosis? (4 marks)
- genetically identical cells
- increase cell number
- asexual reproduction
- to replace cells
why were the cells on the slide stained?
to make chromosomes visible
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)
- cancer cells have damaged DNA
- p53 is not made
- cell with faulty DNA completes cell cycle
- uncontrolled division leads to cancer
describe what happens in anaphase (2 marks)
The spindle fibres contract
This causes the centromeres divide
This separates the sister chromatids
pulls them to opposite poles of the cell
describe what happens in prophase?
chromosome becomes visible
chromosomes condense and become thicker
nuclear envelope disintegrates
describe what happens in metaphase?
- chromosomes align on the equator of the cell
- spindle fibres attach to the chromosomes by their centromeres.
describe what happens in telophase?
- the nuclear envelope reforms
- spindle fibres break down
-chromosomes uncoil an become longer and thinnre
what occurs in cytokinesis
- cytoplasm divides
- producing 2 new cells
what are the cells like in mitosis
gentically identtical
why does the mass of DNA increase?
cause DNA is replicating
describe the apperance of chromosomes in prophase?
the chromosomes become visible
they condense and
are short and thick
describe the apperance of chromosomes in metaphas?
the chromosomes appear as two sister chromatids joined at the centromere
describe the appearance of chromosomes in anaphase?
centromeres have divided
sister chromatids are separated to opposite pole of the cell
describe the apperance of chromosomes in telophase
- chromosomes beome longer and thin
what is the process in which bacteria able to replicate
binary fission
Descrribe binary fission in bacteria
plasmids and cirular DNA replicate
the move to opposite poles of cell
cytoplasm divides
do viruses undergo cell division
no
what is cancer
uncontrolled and rapid cell divison
Explain why you have to push down hard on the cover slip, but do not push the cover slip sideways. (2 marks)
push hard- to spread the tissue
dont push sideways- to avoid cells rolling together/ breaking chromosomes
explain why you have to push hard on the cover slip
to spread the tissue to one layer of cells thick and allows light to travel through
explain why you shouldnt push sideways on the cover slip?
to prevent chromosomes from breaking
Describe the role of the spindle during mitosis. (2 marks)
-they attach to chromosomes by their centromeres
- they cause the sister chromatids to separate and pull them to opposite poles
explain why the root tip was used to investigate the stages of mitosis (1 mark)
the site of mitosis in the meristem tissue
explain why a stain was used (1 mark)
to distinguish the chromosomes
explain why the root tip was firmly squashed. (1 mark)
A thin layer which allows light to travel through
Explain one advantage of cells lining in the human gut dividing very frequently. (1 mark)
damaged cells are replaced quicker
Describe the role of the centromere in mitosis. (2 marks)
- they hold chromatids together
- spindle fibres attach to centromeres
- allows chromatids to separate to move to opposite poles
Why is mitosis important in the life of an organism. (2 marks)
- asexual reproduction
- to replace cells
- increase cell number
what is the purpose of treatments to treat cancer cells
they disrupt spindle activity
what happens when spindle fibre formation is stoppedd?
no anaphase
spindle fibres are unable to attach to chromsomes via their centromeres
sister chromatids arent pulled to opposite poles
prevents DNA replication
what is the equation for mitotic index?
number of ccells undergoing mitosis / total number of cells
