B2- cells and control 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
State the three stages of the cell cycle:
Stage 1: interphase
Stage 2 : mitosis
Stage 3: cytokenisis
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 ?
- Asexal reproduction
- Growth
- Reapir of damaged cells
- Cell replacement
Why is mitosis important in organisms ?
- Asexal reproduction
- Growth
- Reapir of damaged cells
- Cell replacement
What are the five stages of mitosis?
Prophase
Metaphase
Anophase
Telephase
Cytokenisis
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
● Two genetically identical ‘daughter’ cells
produced
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 can doctors determine from percentile charts?
● 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 diffrentiate at the earlty stages and become specialised
Describe growth in plants
- Cell division can only occur inmeristematic tissue and the rate of cell division is the same the whole 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 are embryonic stem cells?
Stem cells found in very early embryos that are unspecialised and capable of differentiating into any cell type
What si the function of embryonic stem cells?
Enable the growth and development of tissues in human embryos
What is the primary function of adult stem cells?
Replacement of dead cells
Where are stem cells found in plants?
Meristems
Where are meristem tissure found in plants?
In regions of the plant where cells 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 cells 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?
● Donor stem cells removed from embryos
grown in vitro
● Patient’s own stem cells removed from the
umbilical blood before birth
What are the benifits 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 using stem cells in medicine?
● Transplanted stem cells could cause tumours
● Finding suitable stem cell donors is a difficult task
● Stem cells may be rejected by the body (immunosuppressants taken)
● 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
