B2 cell division and mitosis Flashcards
Chromosomes
The nucleus of a cell contains chromosomes made of DNA molecules.
- Each chromosome carries large numbers of genes.
- In body cells the chromosomes are normally found in pairs (one from the father and one from the mother).
Cell division -Mitosis
Mitosis is a type of cell division which is
required for growth and repair. It produces
two identical cells. Cells divide in a series of
stages called:
Stage 1: DNA replication & production of new cell subcellular structures e.g. ribosomes & mitochondria
Stage 2: Mitosis – one set of chromosomes is pulled to each end of the cell and the nucleus divides.
Stage 3:cytoplasm and cell membrane split to form 2 identical cells.
Cell differentiation
As an organism develops, cells differentiate to form different types of cells.
As a cell differentiates it acquires different subcellular structures to enable it to carry out a certain function. It has become a specialised cell.
Cell differentiation in animals vs plants
Cell differentiation in animals
- Most types of animal cell differentiate at an early stage. In mature animals, cell division is mainly restricted to repair and replacement.
Cell differentiation in plants:
Many types of plant cells retain the ability to differentiate throughout life.
Stem cells
A stem cell is an undifferentiated cell that can divide to give rise to many more cells of the same type, and from which certain other cells can arise from differentiation.
Plant stem cells
Meristem tissue in plants can differentiate into any type of plant cell, throughout the life of the plant.
Stem cells from meristems in plants can be used to produce clones of plants quickly and economically.
- Rare species can be cloned to protect from extinction.
- Crop plants with special features such as disease resistance can be cloned to produce large numbers of identical plants for farmers.
Embryonic stem cells
A fertalized egg cell divides to form an embryo.
The embryo is made up of identical cells these are embryonic stem cells. Embryonic stems cells can divide and differeniate form the many different types of specialised cells required in the body.
Stem cells from adult bone marrow
Stem cells from adult bone marrow can form many types of cells including blood cells.
Theraputic cloning
In theraputic cloning, an embryo is produced with the same genes as the patient, stem cells from the embryo are not rejected by the patients body so the may be used for medical treatment.
Theraputic step by step
Human egg cell from donors nucleus is removed and discarded.
Cell from patient - nucleus is removed from patients cells.
This nucleus is then transferred to the donors egg cell.
The cell is stimulated to divide - the cell divides into an embryo.
After 4-5 days stem cells are removed- then cultured for theraputic use.
Embryonic stem cells potential
Stem cells from human embryos can be cloned and made to differentiate into most different types.
They therefore have the potential to be transplanted into patients to treat medical conditions and disease.
They could be used to replace cells that have been damaged or destroyed eg In T1D ,In cases of spinal cord or brain injusry that have led to paralysis
Ethics of cloning
The use of stem cells has potential risks has risks such as transfer of viral infection and some people have ethical or religious objections such as the embryo cannot give consent.
