What Is Cloning?
- Cloning is the production of genetically identical cells or organisms.
- This means the clone has the same DNA as the original despite bypassing sexual reproduction or the fusion of gametes.
Definition
Cloning
The process of producing genetically identical copies of a cell or organism using natural or artificial methods.
How Does Natural Cloning Occur In Animals?
- Identical twinning is a natural form of cloning:
- A single fertilised egg splits into two embryos.
- Each embryo develops independently.
- Both individuals have identical DNA.
Tip
Identical twins are natural clones because they originate from one zygote.
How Does Natural Cloning Occur In Plants?
- Many plants clone through vegetative propagation, where new plants grow from non-reproductive tissues.
- Common methods include:
- Runners, such as in strawberries
- Tubers, such as in potatoes
Hint
- Runners are horizontal stems that grow along the surface of the soil
- Tubers are underground storage organs
How Can Cloning Be Done Artificially In Plants?
- Cuttings
- A stem or leaf is removed from the parent plant.
- It is placed in soil or water to grow roots.
- A genetically identical plant develops.
- Tissue culture
- A small tissue sample is taken from the plant.
- Cells are grown in nutrient-rich, sterile conditions.
- Many identical plants are produced.
Definition
Totipotency
The ability of a cell to develop into any type of cell and form a complete organism.
Tip
- Plant cells are totipotent.
- This is why cloning plants is easier than cloning animals.
How Can Animals Be Cloned Artificially?
- One method involves splitting an early embryo:
- A zygote is first formed by sexual reproduction.
- The embryo begins early cell division.
- The embryo is split into two or more separate cell groups.
- Each group contains identical genetic material.
- Each embryo is implanted into a surrogate mother.
- Identical offspring develop.
- A second method uses genetic material from an adult cell:
- The nucleus is removed from an adult body cell.
- The nucleus is removed from an egg cell.
- The adult nucleus is inserted into the enucleated (removed nucleus) egg cell.
- An electric shock stimulates cell division.
- The embryo develops and is implanted into a surrogate mother.
Definition
Somatic cell nuclear transfer (SCNT)
A cloning technique in which the nucleus from an adult body cell is inserted into an enucleated egg cell to form an embryo.
Note
Method 1 is limited because only a small number of embryos can be produced from one zygote.
Who Is Dolly The Sheep Important?
- Dolly was the first mammal cloned from an adult cell
- Cloned in 1996 using SCNT.
- Proved that adult cells still contain all genetic information.
- Dolly raised scientific and ethical concerns
- Many failed embryos were produced.
- Dolly developed health problems and aged prematurely.
What Are The Risks And Challenges Of Cloning?
- Animal welfare concerns
- High failure rates during development.
- Increased deformities and health issues.
- Reduced genetic diversity: Populations become more vulnerable to disease.
- Human cloning concerns: Identity, consent, and misuse of technology.
- Low success rates: Many embryos fail to develop normally.
- Developmental problems: DNA reprogramming may be incomplete.
Common Mistake
- Assuming cloning is efficient.
- The success rates of cloning are actually very low.
What Are The Advantages And Disadvantages Of Cloning?
| Advantage | Disadvantage |
|---|---|
| Medical research: Identical organisms reduce experimental variables | Low genetic diversity: Increases vulnerability to disease |
| Agriculture: Replication of desirable traits | Animal suffering: High embryo loss and health issues |
| Conservation: Preserving genetic material of endangered species | High cost: Complex and resource-intensive |
Self review
- Define cloning.
- Describe how adult cell cloning works.
- Explain why Dolly the sheep was scientifically important.
- State one advantage and one disadvantage of cloning.
