T2 -Cell Division And Growth Flashcards
(36 cards)
What is the cell cycle
- a series of events that take place in a cell involving cell growth, DNA replication and cell division
- it is described as the lifecycle of a cell
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 the cell cycle that involves cell growth, the synthesis of new organelles and DNA replication
What does DNA replication involve
- Double helix ‘unzips’ exposing two strands
- DNA bases align next to complementary bases on the DNA strands
- complementary base pairs join
- two identical dna molecules formed
What is a chromosome
A linear DNA molecule tightly coiled around proteins
What happens to chromosomes during dna replication
The dna in the arm of each chromosome (chromatid) is replicated
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 four stages of mitosis
Prophase
Metaphase
Anaphase
Telophase
Outline prophase
- DNA condenses, chromosomes become visible
- nuclear membrane disappears
Outline metaphase
Chromosomes line up along the cell equator
Outline anaphase
- spindle fibres attach to each chromosome
- arms of each chromosome pulled to opposite poles
- chromatids separated
Outline 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
- 2 genetically identical daughter cells produces
A cell divides by mitosis once every 2 minutes. Calculate the number of identical cells present after 10mins
10/2 = 5
5 cell divisions have taken place
2 to the power of 5 = 32
What is cancer
- non-communicable disease
- uncontrolled cell division (due to damaged DNA) 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 (e.g foetal length or head circumference) can be compared to the expected values at a certain age
What does the 95th percentile mean
95% of measure to will be below the value of the 95th percentile
What can doctors determine from percentile charts (3)
- Slower growth than normal (below the bottom line)
- faster growth than normal (above the top line)
- abnormal growth (irregular growth patterns)
Describe growth in animals
- cell division occurs in all body cells. It occurs at a slower rate in adults that 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 ability 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’s life.
- meristem if 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 become specialised (have a specific function)
- some genes switch on or off, determining cell type
Why is cell differentiation important
It enables the formation of specialised tissues with specific functions e.g muscle tissue
