Cell cycle, Mitosis and Meiosis Flashcards
What happens during G1
Protein synthesis
Replication of organelles
cell increases in size
What happens during S
Chromosomes are duplicated / DNA is replicated
What happens during G2
Increase in cell size
increase in energy stores
Duplicated DNA from S phase is checked for errors
What is G0
When the cell leaves the cell cycle permanently or temporarily.
Why would the cell leave the cycle?
DNA may be damaged - The cell should no longer divided, so the cell enters a state of arrest.
Age - As you get older you have more cells, therefore by leaving the cycle they can’t replicate, this decreases the chances of problems such as arthritis
Differentiation - Once a cell has specialised it may no longer divided and re-enter the cell cycle.
What is the G1 checkpoint
Makes sure the cell is the correct size
Makes sure the cell has the correct nutrients
Checks DNA for damage before entering S phase
What is the G2 checkpoint
Makes sure the cell is the correct size
Checks if the replicated DNA has any errors after S phase
What is the spindle assembly checkpoint
Checks the spindle fibres are connected to the chromosomes
Uses of mitosis
Asexual reproduction
Growth of Multicellular organisms
Tissue repair
What does it produce?
Two identical daughter cells
What occurs during S phase (mitosis)
The chromatids are. separated via the centromere they must stay together so each can go into a daughter cell
Acronym for the stages of mitosis
People (Prophase)
Must (Metapahse)
Attack (Anaphase)
Teachers (Telophase)
What happens during Prophase of mitosis
- Chromatin begins to coil and condenses to form chromosomes and become visible under the microscope
- The nuclear membrane breaks down
- Microtubules form spindle fibers
- Centrioles move to opposite ends of the poles
- Spindle fibres connect to the centromeres of the chromatins
What happens during Metaphase of mitosis
Chromosomes are pulled to the centre of the cell to form a line called the Metaphase plane where is stays until Anaphase
What happens during Anaphase of mitosis
The centromeres holding the chromatids together pull the chromatids to opposite sides of the cell. They form a ‘V’ like shape making the easily identifiable
What happens during Telophase of mitosis
- The two new set of chromosomes assemble at the end of each pole, and a nuclear envelope forms around them.
- The chromosomes uncoil and a nucleolus forms
- Cytokinesis begins
What is cytokinesis
The actual split off the cell.
What happens in animal cells during cytokinesis
- A cleavage forms at the centre of the cell.
2. The cell surface membrane is pulled inwards by. the cytoskeleton until it fuses in the middle forming two cells.
What happens in Plant cells during cytokinesis
- Vesicles from ht Golgi form where. the metaphase plate was.
- The vesicles eventually fuse together.
- A new cell wall is formed essentially making a new cell.
How many chromosomes are present during mitosis
There are 46 chromosomes throughout however during prophase there are 96 chromatids.
Uses of meiosis
The formation of gametes / sex cells
What is a homologous chromosome
A matching pare of chromosomes, one inherited from each parent.
What does diploid mean
The normal number of chromosomes (46)
What does haploid mean
Half the number of normal chromosomes (23)