B2 Cells Division Flashcards
(32 cards)
What is the role of chromosomes in cells?
Chromosomes carry the genes that contain the instructions for making new cells
What are genes?
A gene is a small packet of information that controls a characteristics of your body. It is a section of DNA. The genes are grouped together on chromosomes.
How many chromosomes do we have in the nucleus of our cells?
46 arranged in pairs of 2. In each pair one is inherited from the father and one from the mother.
What is meant by cells cycle?
They are the stages of cells division
When do cells divide?
Cells divide when:
- an organism grows
- an organism becomes damaged and needs to produce new cells
What happens during stage 1 of the cell cycle?
- This is the longer stage
- Cells grows bigger, increases mass and carry out normal activity
- They replicate their DNA to form 2 copies of each chromosome ready for division.
- They also duplicate the number of cellular substructures
What happens during Phase 2 of the cell cycle?
This phase is called Mitosis
In this phase one pair of chromosomes is pulled to each end of the dividing cell and the nucleus divides
What happens in phase 3 of the cell cycle?
In this stage also the cytoplasm and cell membranes also divide to form two identical daughter cells
How long does the cell cycle last?
It varies (from less of 24hrs to several years)
Before the baby is born and in childhood it is quicker
Also in adults some cells divide rapidly - eg skin cells
When do animal cells generally get specialised?
Most animal cells get specialised early in life. When a baby is born most of his cells are specialised.
Do specialised cells divide by mitosis?
Most of them can but can only produce the same type of cell
What examples of differentiated cells cannot divide at all?
Examples are red blood cells an skin cells. In these cases adult stem cells replace dead or damaged cells
What happens to nerve cells when they are damaged?
They cannot divide and are not replaced by stem cells. So they are not usually replaced once damaged.
When do plant cells differentiate?
Most plant cells can differentiate all through their lives
How does differentiation in plant cells work?
Undifferentiated cells are formed in meristems (these are parts of the stems and roots). In these areas mitosis takes place almost continuously. The cells then elongate and grow before they finally differentiate
What are meristems in plants?
Meristems are parts of the stems and roots where undifferentiated cells are formed
When do plant cells differentiate?
They differentiate once they are in their final position in the plant
Is differentiation in plant cells permanent?
No. You can move cells from one part of the plant to another. Here it can re-differentiate and become a completely new cell.
What is cloning?
It is producing two identical off-springs
Why from a tiny piece of leaf tissue you can get many identical plant clones?
Because in the right conditions a plant cells can become unspecialised and undergo mitosis many times. These cells will then differentiate and form the various tissues needed for a new plant. The plant will be identical to the parent
What is a stem cell?
They are undifferentiated cells
What types of stem cells exist in animals?
- Embryonic stem cells: they are found in the embryo and then differentiate to form all the specialised cells in the body.
- Adult stem cells: some stem cells can also be found in adults. They are mainly in the bone marrow but scientists now think there might be a tiny number also in different tissues in the body (eg blood, brain, muscles and liver)
Where are adult stem cells found?
They are mainly in the bone marrow but scientists now think there might be a tiny number also in different tissues in the body (eg blood, brain, muscles and liver)
Why are stem cells important?
Some cells can divide and replace themselves if damaged but SOME CANNOT. In these case stem cells stay in the tissue for years only to start dividing and creating new cells when needed
