Human Genetics Gene therapy & DNA fingerprinting Flashcards
(68 cards)
what is gene therapy
The treatment of genetic diseases by giving patients healthy/normal functioning copies of (mutated) defective alleles.
what are the three ways of altering the genotype?
- Repair of the gene
- Replacement of a defective gene with a normal one
- Addition of a normal gene leaving the defective one in place
what are the two types of gene therapy?
- somatic gene therapy
- germline gene therapy
what are the somatic cells?
body cells
how does somatic cell gene therapy work?
Copies of a functional gene are inserted directly into the body cells of sufferers.
If the normal gene has been successfully inserted/ taken up by the affected cells and the patient later has a child, since the gene is NOT in the germ-line, the children will NOT inherit the added functioning gene. Can be short-lived and repeated treatments required
what is a germline cell?
sperm/egg/zygote
what does totipotent mean, and give an example?
They can divide & specialise to become any cell within the body
example: egg/sperm/zygote
what is the germ-line?
The germ-line is the genetic information which is passed onto the next generation i.e. the DNA in the egg or sperm / the gametes
how does germline therapy work?
A corrected / functional, gene is inserted into an egg cell that has been fertilised in vitro (IVF).
Embryo then develops, then is re-implanted into mother’s uterus.
If gene transfer is successful, mitosis ensures that every cell in the embryo contains a copy of the corrected gene.
If there are any changes in these gametes then the offspring will inherit them
it crosses generations
what does germ-line therapy provide?
a treatment for an inherited condition that lasts a lifetime.
is germline therapy legal in humans?
NO
what are the problems related to gene therapy?
The problems are how to get the genes to the EXACT cells that need them, and then to make sure they are expressed – transcribed/translated into a protein.
what are vectors and what do they do?
Vectors are carrier molecules
Need vectors to get the normal functional gene into a target cell
what are examples of vectors?
Viruses
Plasmids
liposomes
how do you use adenovirus vectors for gene therapy?
A functional gene is injected into an adenovirus vector, which is used to introduce the modified DNA into a human cell. If the treatment is successful, the new allele will make a functional protein
what are advantages of viral vectors?
- Good at targeting and entering cells
- can target specific cell types - can be modified so they cant replicate and destroy cells
what are disadvantages of viral vectors?
- Can only carry limited size of gene
- May lead to immune response in patients which may cause side effects or block the virus getting to patient’s cells or kill cells once infected
what are the advantages of liposome vectors?
Can carry normal/functional alleles as a plasmid inside the bilayer
Lipid bilayer will fuse with cell surface membrane to deliver contents directly into the cell
Can carry large genes and don’t cause immune response in patients
why are liposomes used as gene therapy?
- Liposomes are spheres made of lipid bilayer
- Can carry normal/functional alleles inside the bilayer
- Lipid bilayer will fuse with cell surface
membrane to deliver contents directly into the
cell
what are vector delivery methods?
- in vivo
- ex vivo
what is ex vivo delivery?
Body cells are removed, copies of functional genes inside vectors are inserted into them and then the transfected cells are put back into the patient’s body.
what does ex vivo delivery work best with?
leukemia,
patient bone marrow cells are extracted, transfected, then replaced
less likely to trigger an immune response
what is in vivo delivery methods?
If a large number of body cells cannot be removed safely, functional genes inside a vector are inserted directly into the affected tissues.
what is in vivo delivery methods used for and how?
cystic fibrosis treatments,
Functional CFTR gene is inserted into a liposome and inhaled to get it to the target cells which are epithelial cells of the lung