T2 -Cell Division And Growth Flashcards
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
What are embryonic stem cells
Stem cells found in very early embryos that are unspecialised and capable of differentiating into any cell type
What is the function of embryonic stem cells
Enable the growth and development of tissues in human embryos
What are adult stem cells
Stem cells that can differentiate into a limited range of cell types e.g. bone marrow stem cells
What is the primary function of adult stem cells
Replacement of dead cells e.g. replacement of red blood cells which only live for 120 days
What are stem cells found in plants
Meristems
Where is meristem tissue found
In regions of the plant where cels are continuously dividing e.g root tips, shoot tips
What are meristematic stem cells
Stem cells found in meristems that are unspecialised and capable of differentiating into any cell type during the life of a plant
How can stem cells be used in medicine
- stem cells collected
- stem cels stimulated to differentiate into specific cell types e.g. heart muscle cells
- specialised cells transplanted into the patient
- used to treat damage or disease e.g. heart disease
Where can embryonic stem cells be collected from (2)
- donor stem cells removed from embryos grown in vitro
- patient’s own stem cells removed from the umbilical blood before birth
What are the 4 benefits of using stem cells in medicine
- treat damage or disease e.g heart disease, type 1 diabetes
- treat diseases that would otherwise be untreatable
- used in scientific research
- growing organs for transplants
What are the risks of stem cell use in medicine (6)
- transplanted stem cells could cause tumours
- finding suitable stem cell donors is a difficult task
- stem cells may be rejected by the body
- potential side effects
- long term risks of using stem cells unknown
- stem cells may become contaminated during preparation and when transplanted transmit infections to the patient, making them sicker
What are the ethical issues related to the use of stem cells in medicine (2)
- the embryos that were used to provide stem cells are destroyed which is seen as unethical and a waste of potential human life
- may lead to the reproductive cloning of humans
