2.1.6Scaling Up

Embryonic and Adult Stem Cells in Animals — OCR Gateway GCSE Combined Science A J250 - Biology Revision Notes & Topical Questions

5 min read 9 parts Lesson 7 of 16

📚 OCR Gateway GCSE Combined Science A J250 - Biology Hub / Topical Revision

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Part 1 of 7Two sources of stem cells

Animals, including humans, have stem cells in different places. Embryonic stem cells come from embryos a few days old, usually spare embryos made during IVF treatment that would otherwise be discarded, or embryos made by therapeutic cloning. Adult stem cells are found in tissues such as bone marrow, skin and the gut lining. Stem cells can also be taken from the umbilical cord blood after birth.

Feature	Embryonic	Adult
Range of cells formed	Almost any cell type	Limited, usually cells of that tissue
Ease of collecting	Requires destroying an embryo	Can be collected from the patient (for example bone marrow)
Rejection risk	Higher if from a donor embryo	None if from the patient
Ability to divide	Divide for a long time in culture	Divide less

Part 2 of 7How stem cells are used in treatment

Stem cells can be grown in culture with the right chemical signals so that they differentiate into the cells needed. The aim is to replace damaged or lost cells. Current and potential uses include:

Bone marrow transplants for blood cancers, using adult stem cells.

Growing nerve cells for spinal cord damage.

Replacing insulin-making cells in type 1 diabetes.

Repairing damaged heart tissue after a heart attack.

In therapeutic cloning the nucleus from a patient's body cell is placed into an egg cell that has had its nucleus removed. The embryo that grows has the patient's genes, so stem cells from it are very unlikely to be rejected.

Part 3 of 7Risks

Tumour formation

Tumour formation because stem cells divide rapidly and may continue dividing after being put into the body.

Viral contamination

Viral contamination viruses in the culture or donor tissue could be passed to the patient and cause disease.

Rejection

Rejection by the immune system when the cells are not from the patient.

Part 4 of 7Ethical and social arguments

For using embryonic stem cells

they could cure or treat serious diseases and improve or save many lives;
- the embryos used are spare ones that would be destroyed anyway;
- early embryos have no nervous system and cannot feel pain.

Against

an embryo has the potential to become a human, so destroying it is wrong to some people on religious or moral grounds;
- the embryos could instead be donated for implantation;
- there is a worry about taking research further to create embryos purely to harvest cells.

Governments therefore regulate this research. Some countries ban it; others, including the UK, allow it only under licence and strict conditions. Adult stem cells raise fewer objections because no embryo is destroyed, but they are less versatile.

Part 5 of 7Writing balanced evaluations

In an evaluation question, give points for and against, and use evidence rather than opinion.

Writing balanced evaluations

Scientific arguments (can it work, is it safe) are separate from ethical ones (is it right).

Science can say whether a treatment works; it cannot alone decide whether it is acceptable.

Weighing the benefit to patients against the status of the embryo is a matter for society.

Part 6 of 7Applying the arguments

Exam questions often give a short statement from a patient group or a religious organisation and ask you to use it.

Applying the arguments

A patient group would stress the potential to cure disease such as Parkinson's or diabetes and to reduce the suffering of people on long transplant waiting lists.

A group with a religious viewpoint may consider that life begins at fertilisation, so an embryo has the right to protection.

A scientist may point out that embryonic stem cells have not yet produced treatments as widely as adult stem cells have, so the argument rests on potential rather than established results.

Applying the arguments

Good answers do the following: identify who benefits and who could be harmed, distinguish scientific from ethical points, use named examples such as bone marrow transplants, and reach a conclusion that is justified, for example that research should be allowed under licence with regulation of how embryos are obtained.

Remember that stem cell treatment differs from reproductive cloning, where an embryo is implanted to produce an individual; this is illegal for humans in the UK.

Practical points matter too: culturing stem cells needs sterile conditions, a nutrient medium and the right growth factors, and scientists must be able to show that cells have stopped dividing and differentiated correctly before use, otherwise a tumour could form in the patient.

Part 7 of 7Exam-style questions

Give two advantages of using adult stem cells from a patient rather than embryonic stem cells. [2]2 marks
A patient with leukaemia has a bone marrow transplant. Explain how stem cells help treat the disease. [3]3 marks
Some people argue that research on embryonic stem cells should be banned. Give one argument for and one against the ban. [2]2 marks

Key terms

Term	Meaning
Embryonic stem cell	Stem cell from a very early embryo able to become almost any cell type.
Adult stem cell	Stem cell found in a mature tissue with a restricted range of cell types.
Therapeutic cloning	Producing an embryo with a patient's genes to obtain compatible stem cells.
Rejection	Attack on foreign cells by the immune system.
Ethical issue	A question of right and wrong that science cannot answer on its own.
Bone marrow	Soft tissue inside bones containing stem cells that make blood cells.

Avoid these mistakes

Giving personal opinion with no reasoning; use reasoned scientific or ethical points.

Saying embryonic stem cells cannot cause rejection; they can unless they are matched or made by therapeutic cloning.

Thinking adult stem cells can become any cell; their range is limited.

Confusing therapeutic cloning (making stem cells) with reproductive cloning (making a whole organism).

Last updated: 20 October 2026