Chapter 6 - Cell Division Flashcards
What are the 2 main stages of the cell cycle of eukaryotic cells?
Interphase + Mitotic Phase
What is Interphase?
The long period in which the cell is not dividing
What is the Mitotic Phase?
The period of cell division - split into 2 stages: Mitosis, where the nucleus is divided, and Cytokinesis, in which the cytoplasm divides and two new cells are produced.
List 3 things that occur during interphase
- Protein Synthesis occurs in cytoplasm.
- mitochondria grow and divide within the cytoplasm.
- normal metabolic processes of cells occur.
What are the 3 stages of interphase?
G1 - cell increases in size
S - (synthesis) - DNA replicated in nucleus
G2 - 2nd growth phase - the cell continues to increase in size, duplicated DNA checked for errors.
What is the G0 phase for?
When a cell leaves the cell cycle, either temporarily or permanently.
Why does the G0 phase occur?
Differentiation - A cell that becomes specialised to carry out a particular function (differentiated) is no longer able to function / divide.
Damaged DNA - damaged cells can no longer divide and enter state of permanent cellular arrest (G0)
What are Checkpoints?
Control mechanisms of the cell cycle
What is the G1 checkpoint?
At the end of the G1 phase, if cell satisfies requirements of checkpoint, then DNA replication (S) is triggered.
What is the G2 checkpoint?
For the cell to pass this checkpoint, it must satisfy a number of requirements, e.g. if DNA has been replicated without error; if these are satisfied, then cell is signalled to begin mitosis.
What is Spindle Assembly checkpoint?
At metaphase in mitosis, where the spindle fibres should have formed - Mitosis cannot proceed until this checkpoint is passed.
What is Mitosis?
The division of the nucleus, ensuring that both daughter cells produced are genetically identical.
True or False - mitosis is necessary for asexual reproduction.
True
How do prokaryotic cells divide?
Binary Fission
What are the four stages of mitosis?
Prophase, Metaphase, Anaphase, Telophase.
What occurs during prophase?
- Nucleolus dissapears
- chromatin fibres condense to form chromosomes
- Protein microtubules form spindle-shaped structures
- centrioles are cylindrical bundles of proteins - they migrate to opposite poles of the cell.
- By the end of prophase, the nuclear envelope has dissappeared.
What occurs during metaphase?
- Chromosomes are moved by the spindle fibres to form a plane in the middle of the cell.
- this is called the metaphase plate.
What occurs during anaphase?
- Centromeres divide, and chromatids are seperated to oppposite sides of cell.
- chromatids form āvā shape due to being dragged by centromeres through liquid cystol.
What occurs during Telophase?
- chromatids have now reached poles and have become chromosomes
- nuclear envelope reforms around them
- cytokinesis can begin.
What is cytokinesis?
The actual division of the cell into 2 seperate cells.
How does cytokinesis work in animal cells?
- Cleavage furrow forms.
- cell-surface membrane pulled inwards by cytoskeleton until it fuses at the middle, creating 2 cells.
How does cytokinesis work in plant cells?
- vesicles created by golgi apparatus fuse with one another to the cell membrane, which divides the cell into 2
- new sections of cell wall form around the new sections of membrane.
Why can plant cells not form a cleavage furrow?
They have strong cellulose cell walls, so it is not possible for them to be manipulated by the cytoskeleton.
