B5. Gene Therapy

Question 1

How does gene therapy work?

Gene therapy involves… to …

How you do this depends on whether the disorder is caused by… or…

How do you treat each of the issues?

What do they both involve? (3)

Answer 1

How does gene therapy work?

Gene therapy involves altering the defective genes (mutated alleles) inside cells to treat genetic disorders and cancer.

How you do this depends on whether the disorder is caused by a mutated dominant allele or two mutated recessive alleles.

• If it’s caused by two mutated recessive alleles you can add a working dominant allele to make up for them - you ‘supplement the faulty ones.
• If it’s caused by a mutated dominant allele you can ‘silence’ the dominant allele (e.g. by sticking a bit of DNA in the middle of the allele so it doesn’t work any more).

They both involve:

  - inserting a DNA fragment into the person's original DNA. 
  - Just like in recombinant DNA technology, you need a vector to get the DNA into the cell 
  - A range of different vectors can be used, e.g. altered viruses, plasmids or liposomes (spheres made of lipid).

Question 2

The two types of gene therapy - Somatic therapy

What does it involve?
What does it not affect?

Answer 2

• This involves altering the alleles in body cells, particularly the cells that are most affected by the disorder.
• Somatic therapy doesn’t affect the individual’s sex cells (sperm or eggs) though, so any offspring could still inherit the disease.

Question 3

The two types of gene therapy - Germ line therapy

What does it involve?

Disadvantage?

Answer 3

• This involves altering the alleles in the sex cells. This means that every cell of any offspring produced from these cells will be affected by the gene therapy and they won’t suffer from the disease.
• Germ line therapy in humans is currently illegal though.

Question 4

Ethical issues surrounding gene therapy (2)

Answer 4

• Some people are worried that the technology could be used in ways other than for medical treatment, such as for treating the cosmetic effects of aging.
• Other people worry that there’s the potential to do more harm than good by using the technology (e.g. risk of overexpression of genes gene produces - too much of the missing protein).