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Nucleus

The part of a cell that controls the cell function and contains the chromosomes.

Sperm

The male sex cell or gamete. The full name is spermatazoan, abbreviated to sperm cell or sperm.

In vitro fertilisation

In vitro fertilisation is a form of infertility treatment where ova are removed from a woman and fertilised outside of the body by sperm. The resulting zygotes are allowed to develop for a few days before one or at most two embryos are returned to the uterus to implant and develop.

Activity: Gene Therapy

Some of the following pieces of information about gene therapies are scientific fact. Some are speculation. Some are opinion. Can you decide which are which? Explain your decisions.

Discussion point

Somatic cell gene therapy has been tried in the quest to cure cystic fibrosis and in research aimed at silencing the gene responsible for Huntington’s disease. Therapy of this sort offers great potential benefits to individual sufferers. If an effective way of getting the healthy genes into their cells so that they can work is found, they will no longer suffer from the symptoms of their disease.

Discussion point

Although somatic cell gene therapy has the potential to help individuals, it does not alter the fact their germ line cells – the eggs and sperm – still carry the damaged DNA. Faulty alleles may still be passed on to their children. These children may be carriers of the genetic disease, or they may be affected themselves.

Discussion point

Germ cell gene therapy effectively involves changing the genes of the germ line – the eggs and sperm – so that faulty genes cannot be passed on.

Discussion point

The easiest way to change the genes in the germ line is to change the genetic information in the fertilised egg immediately after in vitro fertilisation. This could be done by microinjecting the healthy gene into the nucleus of the fertilised egg, or by using gene scissors. The embryo which then developed would not only be free from the genetic disease themselves, they would be free from any risk of passing it on. No-one is yet quite sure what effect such a major change would have on an early embryo and the impact might not become clear until years into the life of the individual.

Discussion point

There is some scientific evidence that early embryos are pretty tough and could probably withstand genetic manipulation. Animal embryos are cloned by breaking apart an embryo which consists of several cells and using each of these cells to grow another identical embryo. The embryos grow into perfectly normal adult animals.

Discussion point

Genetic testing involves taking one cell from an early human embryo and testing it for certain inherited diseases. The healthy embryos which are selected and implanted into their mothers grow into apparently normal, healthy children.

Discussion point

Removing the risk of genetic diseases through genetic manipulation of embryos is very attractive. But it is possible that some parents might pressurise doctors to manipulate an embryo in order to have a child who was not just healthy but good-looking and intelligent too. The idea of trying to produce perfect people, by whatever means, raises concerns for many people because of associations with the eugenics programme in Nazi Germany in the 1930s and 1940s.

Discussion point

If it became possible not just to prevent disease but also to increase life expectancy, make people taller, change their skin colour or intelligence, there would be some people who would be prepared to pay a lot of money to take advantage of such treatment. There would also be people prepared to accept money to do it. This would increase the advantages available to the rich over those available to the poor. This type of selection is currently banned in many countries, including the UK.

Discussion point

A course of in vitro fertilisation costs around £5000. Genetic manipulation of embryos involves IVF as well as the genetic modification itself – it is going to be very expensive. These types of treatment should not be paid for by taxpayers as a whole (through NHS funding) because infertility is not a life-threatening disease. It should be funded by the affected individuals concerned.

Discussion point

If genetic diseases such as cystic fibrosis and muscular dystrophy could be eliminated by germ cell gene therapy, the money saved by not having to care for all the affected individuals could be used to pay for the therapy programme.