Cell division, cell diversity and cellular organisation Flashcards
What is the cell cycle?
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 main phases of the cell cycle?
- interphase
- mitosis
What is interphase divided into?
G1, S and G2
What is mitosis divided into?
Prophase, metaphase, anaphase, telophase
What happens during interphase?
- DNA is replicated and checked for errors
- protein synthesis
- mitochondria and chloroplasts grow and divide, increasing in number
- normal metabolic processes occur eg respiration
What happens at G1?
- cell growth
- cellular components
- protein synthesis
What happens in the S phase if interphase?
Each of the chromosomes are duplicated
What happens at G2?
- cell size increases
- the cell checks the duplicated chromosomes for errors, making any repairs that are needed
- energy store increases
What happens at cytokinesis?
Cytoplasm divides
What happens at G0?
When the cells leave the cycle either temporarily or permanently
Why do cells enter G0?
- differentiation
- cells may be damaged
- apoptosis
Give an example of a cell that can be stimulated to go back into the cell cycle after G0?
Lymphocytes
Why is it important that the cell cycle is controlled?
To ensure the fidelity of cell division
What are the roles of checkpoints in the cell cycle?
They monitor and verify whether the process at each phase has been accurately completed before the cell is allowed to progress to the next phase
What does the G1 checkpoint check for?
- cell size
- nutrients
- growth factors
-DNA damage
What does the G2 checkpoint check for?
- cell size
- DNA replication
What does the spindle assembly checkpoint check for?
Chromosomes attachment to spindle
Why do cells divide by mitosis?
- growth
- repair
- asexual reproduction
What does asexual reproduction?
- fungi
- plants
- some animal cells
What is a centromere?
A structure on a chromosome that allows two chromatids to attach to each other or to the spindle during cell division
What is a chromatid?
One of two halves of a replicated chromosome
What is a homologous chromosome?
A pair of chromosomes of the same length and carrying the same genes in the same positions- one is maternal and one is paternal
What happens before prophase?
DNA combines with histone proteins to form a dense complex chromatin
What happens during prophase?
- chromatin fibres coil and condense to form visible chromosomes
-nucleolus disappears - nuclear envelope starts to break down
- microtubules form the spindle that links the poles of the cell
- spindle attaches to centromere to move chromosomes to centre of cell
- nuclear envelope disappears