5.4 Cloning

REVISION NOTES

IGCSE Edexcel Biology

5.4.1B Describe the process of micropropagation (tissue culture) in which explants are grown in vitro

Micropropagation:

Process of growing small pieces of plant tissue in a nutrient rich medium in vitro
- Grown in agar or petri dish
- Stimulates growth
Plants are genetically identical to parent plant

Process of micropropagation:

Cells or small pieces of plant tissue are extracted from a plant
1. These small pieces are known as explants
Sterilise the explant by rinsing it with water
Transfer the explants to a sterile agar or petri dish
The explant will grow into a small bundle of cells known as callus
Transfer each individual callus to another growth medium containing nutrients and growth hormones
The callus should then develop roots, stems and leaves
1. Callus with developed plant organs is called a plantlet
Transfer each plantlet to its own pot to grow the plant

5.4.2B Understand how micropropagation can be used to produce commercial quantities of genetically identical plants with desirable characteristics

Uses of micropropagation:

Preservation of rare plant species
Mass production of plant with desirable characteristics for commercial use
- Increase yield
- Reproduce plant at a faster rate
- Cost effective
- Controlled environment ensures higher success rate in plant formation
Create disease resistant plant species

5.4.3B Describe the stages in the production of cloned mammals involving the introduction of a diploid nucleus from a mature cell into an enucleated egg cell, illustrated by Dolly the sheep

Process of cloning mammals:

An adult female sheep was first cloned to create Dolly the sheep
The following process was used to create the clone:

1. Remove the nucleus of an unfertilised egg cell
  1. Removal of nucleus is called enucleation
2. Insert the nucleus of a cell from the adult body into the enucleated egg cell
3. Stimulate the nucleated egg cell to divide by providing an electric shock
4. The nucleated egg cell will undergo mitosis to form an embryo
5. The embryo is now genetically identical to the parent cell
6. Insert the embryo in a surrogate mother’s womb once it develops into a ball of cell
7. The embryo continues development in the womb of the surrogate mother
  1. The rest of the pregnancy proceeds as usual

5.4.4B Understand how cloned transgenic animals can be used to produce human proteins

Producing human proteins:

Produce a transgenic animal
- Transgenic animals contain genes from a different species
- Allows them to produce proteins coded by that gene
- These proteins could be useful compounds

Transgenic animals can be cloned to mass produce proteins of interest such as:
- Antibodies
- Antibiotics
- Insulin
- Blood clotting factor IX
Cows are generally used as proteins can be produced within their milk
- Increased ease of production, extraction and distribution