Flashcards in SB2 Deck (63)
What is mitosis?
A type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus.
What are the main stages of the cell cycle?
What’s the prophase?
The chromosomes condense, getting shorter and fatter. The membrane around the nucleus breaks down and the chromosomes lie free in the cytoplasm.
What’s the metaphase?
The chromosomes line up at the centre of the cell.
What’s the anaphase?
Cell fibres pull the chromosomes apart.
The two arms of each chromosomes go to opposite ends of the cell.
What’s the telophase?
Membranes form around each of the sets of chromosomes.
These become the nuclei of the two new cells - the nucleus has divided.
What happens in the cytokinesis process?
Before the telophase ends, the cytoplasm and cell membrane divide to form two separate cells.
What’s the interphase?
In a cell that’s not dividing, the DNA is all spread out in long strings. Before it divides, the cell has to grow and to increase the amount of subcellular structures such as mitochondria and ribosomes.
It then duplicates its DNA - so there’s one copy for each new cell. The DNA is copied and forms X shaped chromosomes. Each ‘arm’ of the chromosomes is an exact duplicate of the other.
What has been produced at the end of mitosis?
The cell has produced two new daughter cells.
Each daughter cell contains exactly the same sets of chromosomes in its nucleus as the other daughter cell - they’re genetically identical diploid cells.
They’re also genetically identical to the parent cell.
What is growth?
An increase in size or mass.
What are the processes that cause plants and animals to grow and develop?
1. Cell differentiation
2. Cell division
3. Cell elongation
What is cell differentiation?
The process by which a cell changes to become specialised for its job. Having specialised cells allows multicellular organisms to work more efficiently.
What is cell division?
What is cell elongation?
This is where a plant cell expands, making the cell bigger and so making the plant grow.
How does animal growth happen?
It happens by cell division.
Animals tend to go while they’re young, and then they reach full growth and stop growing.
When you’re young, cells divide at a fast rate but once you’re an adult most cells divide for repair.
How does plant growth happen?
Growth in height is mainly due to cell elongation
Cell division usually just happens in the tips of the roots and shoots.
Plants often grow continuously - they continue to differentiate to develop new parts.
Give an example of uncontrolled cell division
What controls the rate at which cells divide by mitosis?
Controlled by the chemical instructions (genes) in an organisms DNA.
What causes a cell to divide uncontrollably?
If there’s a change in one of the genes that controls cell division.
This can result in a mass of abnormal cells called a tumour.
If the tumour invades and destroys surrounding tissue it’s called cancer.
What are percentile charts used for?
Used to monitor growth.
They’re used to assess a child growth over time, so that an overall pattern in development can be seen and any problem highlighted (obesity, malnutrition, dwarfism).
What are undifferentiated cells called?
What can stem cells do?
Depending on what instructions they’re given, stem cells can divide by mitosis to become new, which then differentiate.
Why are stem cells important?
For the growth and development of organisms.
Where are stem cells found?
In early human embryos
Adults - bone marrow
What do meristems contain?
Plant stem cells
What are found in meristem?
In plants, the only cells that divide by mitosis are found in plant tissues called meristems.
What do meristems produce?
They produce unspecialised cells that are able to divide and form any cell type in the plant.
The unspecialised cells go on to form specialised tissues like xylem and phloem.
Explain how Stem cells can be used in medicines?
1. Doctor already use stem cells to cure some disease (sickle cell anaemia).
2. Scientists have experimented with extracting stem cells from from very early human embryos and growing them. Under certain conditions the stem cells can be stimulated to differentiate into specialised cells.
3. It might be possible to use stem cells to create specialised cells to replace those which have been damaged by disease or injury. (New cardiac muscles for someone with heart disease).
Before scientists can use stem cells for potential new cures lots of research needs to be done.
Name the risks with using stem cells?
1. Tumour development - stem cells can divide very quickly, creating a tumour.
2. Disease transmission - viruses live inside cells. If donor stem cells are infected with a virus it could pass on to the patient.
3. Rejection - if the transplanted cells aren’t grown using the patients own stem cells, then their body might recognise the cells as foreign and trigger an immune response to get rid of them.