Cell cycle Flashcards
Mitosis, meiosis, stem cells
What is the cell cycle?
It is a highly ordered sequence of events that takes place in a cell, resulting in division of the cell and the formation of two genetically identical daughter cells
What are the two stages of cell cycle?
Interphase and mitotic phase
What is interphase?
It is normally referred to as the “resting stage” of the cell as the cell is not actively dividing. however, the cell is performing its function of that particular cell type
What are the three stages interphase?
G1, S and G2
What happens during the G1 phase?
The cell grows in size
The organelles replicate
Protein synthesis takes place (translation and transcription happens)
What happens during the S phase?
DNA is replicated and;
Chromosomes are synthesized
What happens during the G2 phase?
Energy stores are increased
Cell continues to grow in size
Damaged chromosomes are repaired
What is the mitotic phase?
It is the period of cell division because the cell divides into two
What are the 2 stages in the mitotic phase?
Mitosis and Cytokinesis
What is the G0 phase?
It is when the cell leaves the cell cycle either permanently or temporarily
What are the 2 reasons why cells enter the G0 phase?
- Differentiation: It is when a cell becomes specialised to perform a particular function which makes the cell unable to divide so it stays in G0 permanently
- DNA has become damaged: Senescent cells are cells that are not able to divide anymore and these cells increase as we age
What are checkpoints?
Checkpoints are the control mechanism of the cell cycle that monitor and verify whether the processes at each phase of the cell cycle has been accurately completed before the cell is allowed to progress into the next stage
Where are the 3 checkpoints in the cell cycle?
G1 checkpoint- at the end of G1 phase before entry into the S phase
G2 checkpoint- at the end of G2 phase before entry into the mitotic phase
Metaphase checkpoint
What is checked in the G1 checkpoint?
- Cell has grown in size
- DNA damage
What is checked in the G2 checkpoint?
Energy stores are increased
DNA damage & replication
Cell growth
What is checked in the metaphase checkpoint?
This checks that the chromosomes are assembled correctly on the mitotic spindle
Explain, with reference to the structure and function of proteins, the importance of G2 checkpoint. (3 marks)
DNA has been checked for errors(1) change in sequence of bases is a mutation (1) which leads to change in amino acid sequence(1) function of protein is dependent on its tertiary structure(1) which is dependent on the primary structure(1)
What is mitosis?
It is the process of NUCLEAR DIVISION that occurs before a cell physically divides into two daughter cells
Importance of Mitosis
- It is a form of asexual reproduction which is the production of genetically identical offsprings in multicellular organisms including plants, animals and even fungi
- It also provides new cells for growth and repair of tissues and replacements of cells with short lifespan
What is a centromere?
It is a region where two chromatids are joined together
What are the 4 stages of mitosis?
PMAT
Prophase
Metaphase
Anaphase and
Telophase
What happens in the prophase stage?
- Chromatin coils up and condenses to become chromosomes, which take up stain to become visible under the light microscope
- The nuclear membrane starts to break down
- The nucleolus disappears
- Centrioles move to opposite poles of the cell and help in the formation of spindle fibres
- Spindle fibres then attach to the centromeres of each chromosome and move it to the center of the cell
What happens in the metaphase stage?
The chromosomes are pulled to the center of the cell and are lined up at the equator of the cell
What happens in anaphase stage?
The centromeres divide and the spindle fibres shorten.
This shortening pulls the sister chromatids to opposite poles of the cell
