Cloning

What does grown in vitro mean?

Grown in glass, often referring to the glassware in lab procedures

Describe the process of micropropagation (tissue culture).

1. Tips of stems/ roots/ side shoots are removed from the plant to be cloned - explants

2. Explants are trimmed to about 0.5-1.0 mm

3. Then, explants are washed in mild bleach to kill any microorganisms

4. In sterile conditions, explants are placed in an agar medium that contains nutrients (glucose, nitrogen source or nitrates) and plant hormones to encourage cell division and growth

5. Cells in explant divide by mitosis to form a callus

6. When there are many cells, they are separated into smaller pieces again and grown under sterile conditions

7. Some explants are put on different growth mediums with different concentrations of plant hormones to encourage the cells to differentiate and produce roots, shoots and leaves

8. The grown roots and shoots (plantlets) are transferred to greenhouses and transplanted into compost

9. Greenhouses are kept very moist to reduce water loss

What are the advantages of micropropagation?

• Large numbers of genetically identical plants can be produced rapidly

• Species that are difficult to grow from seed or cuttings can be propagated instead

• Plants can be produced at any time of the year

• Large number of plants can be stored easily - kept in the cold at early stages of production and developed when needed

• genetic modifications can be introduced into thousands of plants quickly after modifying only a small amount of plants

Why are cloning animals beneficial?

• allows reliable and quick production of animals with desirable characteristics

• helps build population of rare animals that are threatened with extinction

Describe the stages in the production of cloned mammals.

1. Haploid nucleus of an unfertilised egg is removed, forming an enucleated egg cell

2. Diploid nucleus from a mature body cell of a donor fuses with the enucleated egg cell by an electric pulse

3. A second electric pulse is then used to trigger the cell division of mitosis to produce an embryo

4. The developing embryo is implanted in the uterus of a surrogate mother

5. The surrogate mother then gives birth to a baby who is identical to the donor

What is a real-life example of cloned mammals?

Dolly the sheep

What are some concerns of reproductive cloning using the example of Dolly the sheep?

• Technique has a low success rate (Dolly was produced after 237 attempts)

• As the body cell of the donor most likely has already lived a few years, the embryo tends to not develop normally, meaning a shorter lifespan

• Often an increase in birth size

• Defects in organs like the heart, liver, kidney and brain

• Their immune system may not function as it should

What is therapeutic cloning?

It is when cells are taken from an early embryo (before 10 days) so before the cells have started to differentiate and uses embryonic stem cells for disease treatment