Process of Gene Therapy
What is gene therapy used for?
To correct defective genes that cause diseases or disorders in affected organisms, most often humans.
What is a vector?
Any agent that can insert its foreign DNA into a cell. Plasmids and viruses are some types of vectors.
What are three obstacles to gene therapy?
Any three: Gene vectors, delivery of the gene, gene expression, high costs, technological limitations, regulatory and ethical issues.
How is gene therapy regulated?
Administrations of healthcare and nutrition approve gene therapy before it can be widely used.
Who was Dolly?
Dolly was the first cloned mammal.
How are normal genes transferred to the target cell?
Via a vector that infects the target cell so that the normal DNA is inserted into the target cell genome.
What was the vector used for the treatment of Bubble Baby Disease?
Retrovirus
Why is technology a limitation to the development of gene therapy?
Modern gene-editing technology does not have the precision to modify the defective genes of every disease.
Why may a gene therapy not be accessible for every individual affected with a disorder?
Gene therapy is expensive and thus is inaccessible for some of its target patients.
What caused complications in the treatment of Bubble Baby syndrome? What was the complication?
A retroviral vector activated cancer-causing genes, resulting in 4 patients developing leukemia.
What is the first step in the process of gene therapy?
Scientists modify or remove the viral DNA in the vector, then insert normal human genes into the virus so that the normal genes are incorporated into the DNA of the virus. This occurs outside of the body.
Why are vectors required for gene therapy to take place?
Vectors carry normal genes and deliver them to the genome of the target cell which has a defective gene that causes disease.
Why may inserted genes not be incorporated into the target cell genome?
An inserted gene that does not work for the duration of the target cell’s life will not be incorporated into the target cell genome. As mitosis is performed, some cells will be created with the correct gene while others will be created with the defective gene.
Why may a developed gene therapy be rejected by healthcare administrations?
The gene therapy is considered unsafe because it has adverse effects on test subjects and these effects are considered more harmful than the disorder the therapy treats.
How can gene therapy be used to improve vision in subjects with inherited blindness?
An eye syringe can be used to inject viruses that carry the normal gene behind the pigment cell layer of the eye. When the normal genes are incorporated into the cells, normal function is restored to the eye which improves vision problems.
Through what method is gene therapy introduced into the body of the organism carrying the target cells?
The vector may be injected into tissues or the bloodstream.
What condition must be met in order for a virus to be considered an effective vector?
The virus must deliver genes to the target cell genome. For example, the vector for a genetic disorder impacting the respiratory system should be able to deliver correct genes to the lungs.
What challenge(s) can be faced involving delivering correct genes to defective genomes?
Permanent insertion of the normal gene into the target cell’s genome is not guaranteed due to mitosis.
The unintentional insertion of a normal gene into another gene sequence is another form of unsuccessful delivery of genes.
Why is effective gene therapy sometimes uncertain?
Refer to the obstacles to gene therapy: Gene vectors, delivery of the gene, gene expression, high costs, technological limitations, regulatory and ethical issues.
In addition, effective gene therapy often requires hundreds of trials until a predictable and constructive outcome is reached.
Who was Jesse Gelsinger and how was his experience linked to the development of gene therapy?
Jesse Gelsinger was an 18-year-old treated for OTCD who underwent a severe immune response against an implanted gene. Since Gelsinger’s death, gene therapy has successfully treated OTCD in mice and later in 11 human patients.
Why can’t plasmids be used as vectors for humans during gene therapy?
Plasmids can only carry genes into bacterial cells; they cannot infect mammals, like humans.
Why can vectors sometimes cause immune responses?
Vectors are viruses used to deliver correct genes to defective genomes. They can trigger immune responses as the immune system attacks any foreign body, including viruses.
What is it called when a gene does not permanently insert into the target cell’s genome?
A non-integrating gene.
Mosaicism.
How was the regulation of gene therapy involved in the OTCD treatment of Jesse Gelsinger?
Federal regulators fined the lead scientist in Gelsinger’s treatment because he neglected complications in other test subjects.
How was Dolly’s gene therapy different from typical gene therapy involving defective genes?
The concept of the “vector” was different. Normal gene therapy typically involves a virus as the vector to carry correct genes to defective genomes, however an enucleated, unfertilized egg was used to birth Dolly from the genetic information of another sheep.