Cell Division and Growth PMT Flashcards
What is the cell cycle?
- A series of events that take place in a cell involving cell growth, DNA replication and cell division
What are the 3 stages of the cell cycle?
Stage 1 - interphase
Stage 2 - mitosis
Stage 3 - cytokinesis
What is interphase?
The longest stage of cell cycle that involves cell growth, the synthesis of new organelles and DNA replication.
What does DNA replication involve?
- DNA bases align next to complimentary bases on the DNA strands
- Complementary base pairs join
- Two identical DNA molecules form
What happens to chromosomes during DNA replication?
The DNA in the ‘arm’ of each chromosome is replicated
What is a chromosome?
A linear DNA molecule tightly coiled around proteins.
What is mitosis?
A form of cell division that produces two diploid ‘daughter’ cells; both genetically identical to the parent cell.
Why is mitosis important in organisms?
- Asexual reproduction
- Growth
- Repair of damaged cells
- Cell replacement
State the four stages of mitosis
- Prophase
- Metaphase
- Anaphase
- Telophase
Describe Prophase
- DNA condenses, Chromosomes become visible
- Nuclear membrane disappears
Describe metaphase
- Chromosomes lineup along the cell equator
Describe anaphase
- Spindle fibres attach to each chromosome
- ‘Arms’ of each chromosome pulled to opposite poles
- Chromatids separate
Describe telophase
- Nucleus of the cell divides
- New membrane forms around each set of chromosomes
What does cytokinesis involve?
- Division of the cell membrane and cytoplasm
- Two genetically identical daughter cells produced
What is cancer and how is it formed?
- Non-communicable disease
- Uncontrolled cell division results in the formation of a primary tumour
- Tumour cells break off and spread to other tissues forming secondary tumours
What are percentile charts?
- A chart used to monitor growth
- Measurements can be compared to the expected values at a certain age
What does the 95th percentile mean?
95% of measurements will be below the value of the 95th percentile
What can doctors determine from percentile charts?
- Slower growth than normal
- Faster growth than normal
- Abnormal growth
Describe growth in animals
- Cell division occurs in all body cells. It occurs at a slower rate in adults than in younger animals as growth stops and cell division is only required for replacement and repair.
- Most cells differentiate at an early stage and become specialised. Some adult stem cells retain their abilities to differentiate.
Describe growth in plants
- Cell division can only occur in meristematic tissue. The rate of cell division remains the same throughout a plant life.
- Meristematic stem cells can differentiate into any cell type for as long as the plant lives
- Cell elongation occurs in all cells. Cells expand and enlarge enabling growth of the plant
What are stem cells?
Cells that are unspecialised and capable of differentiating into a range of different cell types
What is meant by differentiation?
- The process by which stem cells have become specialised
- Some genes switch on or off, determining cell type
Why is cell differentiation important?
It enables the formation of specialised tissues with specific functions
What are embryonic stem cells?
Stem cells found in very early embryos that are unspecialised and capable of differentiating into any cell type
