Gene Therapy Flashcards
what is the definition of gene therapy?
-the possibility of inserting functional donor alleles into human cells that are not functioning due to the presence of a single defective allele
what are two diseases caused by the presence of a single defective gene in humans? what type of allele is defective
-cystic fibrosis
-muscular dystrophy
-the recessive allele
what has to be present for the cystic fibrosis disease to be expressed?
-both recessive alleles at the gene locus
what has to be present for the muscular dystrophy disease to be expressed?
-a single recessive allele on the single X chromosome in males
what are the two types of gene therapy?
-somatic gene therapy
-germ-line gene therapy
what is the process of somatic gene therapy, what does it involve? at what stage of life ins this used?
-it only targets affected tissues
-used when the condition is specific and easily reached in parts of the body e.g. the lungs
-can be used at any stage of life
what does the process of germ-line gene therapy, what does it involve? at what stage of life is this used?
-involves replacing the defective gene in a fertilised egg
-all cells of the developing individual are normal and there is no issue with targeting affecting tissues in the body
-stops defective gene from being passed on to future generations
what is the main type of gene therapy that is currently used and why?
-somatic therapy
-germ-line us beyond current technology and raises many ethical and moral issues
what are the 3 methods used as vectors to transfer functional DNA into a recipient cell?
-adenoviruses
-retroviruses
-liposomes
what are adenoviruses? how are adenoviruses used as a vector to transfer DNA into tis recipient cell? what are the disadvantages of adenoviruses?
-viruses that cause respiratory infections
-used to transfer the DNA into lung epithelial cells
-before this occurs they have to have their “disease causing” genes removed, and the donor DNA must be spliced in
-it is hard to get rid of the disease causing genes without affecting the genes that allow it to transfer DNA, they can also cause infections also some people are immune to adenoviruses meaning it cannot penetrate the lung cells for transfer
how are retroviruses used?
-used as target host cells
-when host cells are affected by retrovirus its own RNA/ donor RNA is converted into DNA (reverse transcriptase)
-this DNA can then replace the defective DNA in the recipient cell
what are liposomes? how are they used in gene therapy?
-they are artificial lipid vesicles which contains donor DNA
-the lipid coating protects DNA and helps it bind to target cells
-the coat also means it is easier to pass through the lipid part of the bilayer and they dissolve into each other and the donor DNA is released
once the donor DNA is in the target cells what are the 2 ways in which it can function?
-it can be incorporated into the host DNA
-or can function as its own independent DNA
what are episomes?
-the donor DNA units that function independently in the nucleus and are not incorporated into the targets cells own DNA
what are some of the difficulties of gene therapy? 4 reasons
-treatment is often short lived
-it is hard for it to target all the affected areas in the body for a particular condition
-offspring of treated individuals may still be affected
-may be attacked as foreign cells- cause an immune response which can prevent the DNA being “switched on”
what is cystic fibrosis caused by?
-the presence of both recessive alleles
what protein is affected by cystic fibrosis and how is it affected?
-CFTR
-causes mucus build up in the lungs which affects gas exchange
