14.6 Adult Cell Cloning

A free GCSE Biology lesson for AQA (8461) from OBA School: the steps of adult cell cloning, why the clone matches the body-cell donor, and its uses and problems. Watch the video, read the explanation and worked examples, then try the revision questions. You can work through the full lesson, with every video, practice quizzes and printable worksheets with mark schemes, in our free online course.

What you will learn

• Describe the steps of adult cell cloning
• Explain why the cloned animal is genetically identical to the donor of the body cell
• Give uses of adult cell cloning
• Explain the problems and limits of adult cell cloning

Key words

• Adult cell cloning: Making a clone of an adult animal by putting the nucleus from one of its body cells into an egg cell.
• Nucleus: The part of the cell that contains the genetic material (chromosomes).
• Unfertilised egg: An egg cell that has not been joined by a sperm.
• Electric shock: Used to stimulate the egg cell to start dividing, forming an embryo.
• Host mother: The female whose womb the embryo is placed in. She gives birth, but is not genetically related to the clone.

The steps of adult cell cloning

Method

1. The nucleus is removed from an unfertilised egg cell.

2. The nucleus from an adult body cell, such as a skin cell, is inserted into the empty egg cell.

3. An electric shock stimulates the egg cell to divide and form an embryo.

4. The embryo cells contain the same genetic information as the adult body cell.

5. When the embryo has developed into a ball of cells, it is inserted into the womb of an adult female (the host mother) to continue its development.

Whose clone is it?

Almost all of an animal’s genes are in the nucleus. The egg cell’s own nucleus was removed, so the only nuclear genes in the embryo came from the body cell. The new animal is a clone of the animal that gave the body cell – not of the egg donor or the host mother.

Worked example: three sheep

A nucleus from a skin cell of a black-faced ram is put into an empty egg cell from a white-faced ewe. The embryo grows inside a third, speckled ewe. What will the lamb look like?
The genes come from the black-faced ram’s nucleus.

Answer: a black-faced male lamb, genetically identical to the ram

History: The first mammal cloned from an adult body cell was Dolly the sheep, born in Scotland in 1996.

Uses of adult cell cloning

• Copying animals with very valuable characteristics, e.g. champion horses or high-yield cattle.
• Making many copies of a genetically engineered animal, e.g. one that makes a useful medicine in its milk.
• Helping to save endangered species, using body cells stored from rare animals.
• Research: understanding how cells become specialised and how genes are switched on.

Worked example: success rate

In a cloning project, nuclei were put into 180 eggs. 24 grew into embryos and 3 healthy lambs were born. What percentage of the eggs gave a lamb?
3 ÷ 180 × 100 = 1.67% (only about 1 egg in 60)

Answer: 1.67% (3 s.f.)

Problems with adult cell cloning

• Low success rate; Why it matters Many eggs and embryos fail, so it is slow and very expensive.
• Health of clones; Why it matters Some cloned animals have had health problems; long-term effects are still being studied.
• Less variation; Why it matters Clones are genetically identical, so one disease could affect them all.
• Ethical concerns; Why it matters Some people worry about animal suffering, or that it could lead to human cloning (see 14.7).

• Starting point; Embryo transplant (14.5) An embryo made by sexual reproduction; Adult cell cloning A body cell from an adult
• Clone of…; Embryo transplant (14.5) each other only; Adult cell cloning the adult that gave the body cell
• Do we know what it will be like?; Embryo transplant (14.5) No – a new mix of alleles; Adult cell cloning Yes – same genes as a known adult

Common mistakes

• Saying the nucleus is removed from a fertilised egg. It is an unfertilised egg.
• Saying the clone is identical to the egg donor or the host mother. It matches the body-cell donor.
• Saying the electric shock fertilises the egg. It only stimulates the egg to start dividing.
• Mixing up adult cell cloning with embryo transplants.

Revision questions

Try these, then check your answers below each one.

Question 1. What is the first step in adult cell cloning? (Choose from: An embryo is split into separate cells, The nucleus is removed from an unfertilised egg cell, The nucleus is removed from a fertilised egg cell, An electric shock is given to a skin cell.)

Answer: The nucleus is removed from an unfertilised egg cell

Working: The nucleus is removed from an unfertilised egg; then a body-cell nucleus is inserted.

Question 2. What is used to stimulate the egg cell to start dividing in adult cell cloning?

Answer: electric shock

Working: An electric shock stimulates the egg cell to divide and form an embryo.

Question 3. True or false? The cells of the cloned embryo contain the same genetic information as the adult body cell.

Answer: True

Working: True. Its only nucleus came from the body cell, and mitosis copies the DNA exactly.

Related lessons

• Previous lesson: 14.5 Cloning
• Next lesson: 14.7 Ethics of Genetic Technologies
• In this chapter: 14.1 Variation
• In this chapter: 14.2 Evolution by Natural Selection
• In this chapter: 14.3 Selective Breeding

Continue in the full course

This lesson is section 14.6 (AGCBH1406) of our free GCSE Biology course for AQA. In the full course you get every video for this section, a self-marking practice quiz, a printable worksheet with a mark scheme, chapter tests, and your progress saved. Go to the full GCSE Biology course.