Stem Cells and Therapeutic Cloning
Stem cells are undifferenciated cells which can be made to differentiate into other types of cell.
They are found in human embryos and adult bone marrow.
An embryo is produced with the same genes as the patient. Stem cells from the embryo will not be rejected by the patient's body and so can be used for medical treatment.
Cloning Plants - Cuttings
A cutting is taken from a plant and put in rooting hormone. It is covered with a polythene bag to keep it warm, before being planted.
Possible as plant cells retain ability to develop into any type of cell
- Cheap and Easy
- Seasonal, unless kept in a controlled environment
- Limited number of cuttings can be taken from one plant.
Cloning Plants - Tissue Culture
Leaf cells are taken from a plant explant and cultured into a callus (small mass of stem cells). It is kept in a nutrient agar and given rooting hormones before being planted.
- Thousands can be formed from one plant
- Expensive as it must be sterile and needs nutrients
Cloning Animals - Embryo Transplants
High quality cow given fertility drugs to super-ovulate and is artificially inseminated with sperm taken from a high yield bull. Zygotes develop into embryos in cow and removed from uterus. Embryos are split into several smaller embryos, each of which can grow into a new calf. Embryos are then placed in uteruses of foster mothers.
- Cows could produce up to 30 offspring per year, compared to around 8 per lifetime
- Calves can all be of high quality
- Expensive (hormones, transport, equipment)
- Could lead to cloning in humans
- Cows have no choice
Cloning Animals - Adult Cell Cloning
Adult Cell Cloning
Body cells are taken from one sheep, while another is given FSH to superovulate and its egg cells are collected. The nucleus is removed from the egg cell and replaced with the nucleus from the body cell. A tiny electric shock stimulates cell to start dividing to form embryo cells which grow into an embryo in vitro. This is implanted into a surrogate mother and the lamb born is a clone of the first sheep.
- Can be genetically engineered to produce useful proteins in hormones
- Bring back extinct species/save animals from extinction
- Could be abused (cloning of human babies)
- Reduces variety which means that the population is less likely to adapt to any changes
- Often unreliable
- Desired gene is cut out of DNA using an enzyme
- This is inserted into a vector (usually bacteria plasmid)
- It is then inserted into the DNA of the recipient cell
- This multiplies many times to produce clones.
- Could prevent disease/detect hereditary disease
- Desired characteristics can be shown
- Increase genetic diversity
- Moral issues (do we have the right to manipulate nature)
- May have unknown consequences
Genetically Modified Crops
- Increase size of crop
- Resist pests/aphids
- Resist pesticides/herbicides
- Can fix their own nitrogen
- Longer shelf life
- Resist drought/flood
- Increase nutritional value
- Could cross-pollinate with weeds
- Uncertainty about long term effects of eating GM crops