Gene therapy

What is somatic therapy?

Altering alleles in body cells. Offspring could still develop the disorder as sex cells are unaffected. Temporary solution as cells have limited life and will ultimately be replaced by stem cells

What is germ line therapy?

Altering alleles in sex cells. Every cell of any offspring produced will be affected by gene therapy and won’t develop the disorder. Currently illegal in humans

How does gene therapy work?

Adds a functional copy of an allele to cells that have only non-functional copies

How does gene therapy work? (2)

If the genetic disorder is caused by 2 recessive alleles, then a working dominant allele can be added to add the functional protein

If it is caused by a dominant allele,it can be silenced by inserting a DNA fragment into the middle of the allele so it is no longer expressed

How does successful gene delivery occur?

Requires an efficient way to get the DNA into cells and to make it work. Scientists refer to these DNA delivery ‘vehicles’ as vectors

What happens once the DNA is inside the cells of the patient?

It is expressed by the cell’s normal machinery leading to production of the therapeutic protein and treatment of the patient’s disease

What must successful vectors be able to do?

Target the right cells, integrate the genes into the cell. The gene needs to become part of the host cells’ genetic material

What must successful vectors be able to do? (2)

Activate the gene, a gene must go the nucleus and be ‘turned on’, so it is transcribed and translated, avoid harmful side effects

What are challenges with gene therapy?

Delivering a gene into the wrong cell would be inefficient and could also cause health problems for the patient, even once the right cell has been targeted the gene has to be turned on, cells obstruct this process by shutting down genes

What are challenges with gene therapy with the immune system system?

Sometimes new genes introduced by gene therapy are considered potentially-harmful intruders, this could spark an immune response, scientists have to use vectors that don’t trigger an immune response

What are challenges with gene therapy with the cost?

Many genetic disorders that can be targeted with gene therapy are extremely rare, gene therapy often requires another individual

What are positive ethical considerations?

Prolong lives of people with genetic disorders, give people with genetic disorder a better quality of life, carriers could conceive a baby without that disorder, decrease the number of people suffering from genetic disorder

What are negative ethical considerations?

Could be used for alternative treatments, risk of overexpression of genes, it is expensive, multiple treatments necessary, might be difficult to get allele into specific body cells, immune system could identify vectors as foreign bodies, alleles inserted into wrong DNA