What are gene therapy and genetic engineering?

Key facts about gene therapy and genetic engineeringBBC NEWS; BIONET, 2013

Genetic modification involves removing, replacing, altering or adding genes to an organism in some way. Gene therapy is genetic modification used to cure diseases or disorders caused by a genetic problem. The two main types of gene therapy are somatic cell therapy and germ line therapy.

Genetic engineering is genetic modification used to change the make-up of genes so that the capabilities of an organism become beyond what is normal. It can be applied to all types of organisms including bacteria, plants, animals and humans.

What are some of the human uses of genetic engineering and gene therapy?

Somatic cell therapy - this changes the somatic cells, but not the sex cells in the testes and ovaries. Somatic cells make up most of the cells in a human, eg cells in the skin, heart and lungs. When scientists alter the genes in a somatic cell it only affects the individual. The changes will not be passed to their children.

Germ line therapy - this involves changing sex cells (sperm cells or egg cells), and cells in early embryos. These changes to the genes will be passed to the person's offspring. This could be done as therapy, or in order to enhance the individual and their descendants.

Designer babies - procedures that mostly involve checking embryos for disease, disorder or gender. It may be possible in the future to select for other qualities such as strength, beauty or intelligence. Procedures include:

• In Vitro Fertilisation (IVF) happens outside the body, eg used when the parents are experiencing fertility problems or when a genetic disorder might be passed on by the parents.
• Pre-Implantation Genetic Diagnosis (PGD) involves screening embryos at around three days old to check for inherited disorders or genetic diseases, eg cystic fibrosis. PGD can also be used to check embryos to see if any will be a genetic match for a sibling who is already sick.
• Pre-Implantation Genetic Screening (PGS) involves screening embryos to identify gender. In the UK, this is only legal when used for medical reasons, eg with risk of a child inheriting a gender linked disease, eg Duchenne muscular dystrophy.

Saviour sibling - a child who is conceived following embryo screening for a particular tissue type. Their stem cells, taken from umbilical cord blood after birth, can be donated to a sick sibling. This is a form of gene therapy because the technology is used to cure a sick sibling.

Embryology - the use of embryos to learn more about human cells, diseases and disorders. Stem cells derived from embryos created during fertility treatment can be used. They are kept alive so that they produce cells that can be used to produce cures for diseases or disorders.