gene therapy Flashcards
what is gene therapy
the placement of a working copy of a gene into cells that contain non-functioning genes therefore allowing the coding for proteins previously not produced
what are the different methods which can be used for gene therapy
1) somatic cell gene therapy
2) germ-line gene therapy
outline somatic cell gene therapy
replacing faulty genes with correct copies in affected tissues
new genes cant be inherited as only placed in normal body cells
outline germ-line therapy
genes inserted into an embryo or gamete so all new cells formed would contain the new gene and the correction can be inherited
what are the advantages of somatic cell gene therapy
1) relief of symptoms
2) no need for medication
3) prevents the development of cancer
4) doesn’t permanently change the genome
what are the disadvantages of somatic cell gene therapy
1) more than one treatment is required
2) it is hard to integrate gene and for it to work functionally
3) long term effects still unknown
what are the advantages of germ-line cell gene therapy
children born free of genetic diseases
what are the disadvantages of germ-line cell gene therapy
1) fear that it may be used to modify the characteristics of a child
2) permanent modification so may come with some ethical issues
3) may create a new disease
what is DMD
Duchenne Muscular Dystrophy
- a recessive sex-linked condition caused by a deletion too soon in the dystrophin protein so it is not synthesised
what is a deletion
the introduction of a stop codon too soon
outline what happens to an individual with DMD
1) causes progressive muscle weakening
2) muscle fibres break and are replaced by fibrous or fatty tissue
3) life expectancy is around 27 years
4) at around age 20 individuals begin to experience heart and breathing problems
what drug is used to treat DMD
Drisapersen= an antisense oligonucleotide which is a 50 nucleotide sequence complementary to the mutated sequence causing the deletion.
outline how anti-sense oligonucleotides can be used to treat DMD and what the method is called
1) deletion in the gene causes a frameshift mutation resulting in the formation of a STOP codon in an exon preventing the translation of the rest of the gene
2) A small AON is complementary to and binds to the mutated pre-mRNA, masking it, resulting in the mutated exon and the STOP codon being spliced out of the pre-mRNA when introns are removed
3) this restores the reading frame and functional mRNA is formed
4) this is called exon skipping
what are some issues with gene therapy
1) only a small proportion of the introduced gene is expressed
2) patient can initiate an immune response
