Genetic Screening And Gene Therapy Flashcards
Define genetic screening.
Determined the nature of inheritance of genetic condition. Potential to confirm diagnosis; indicate appropriate treatment, allow families to avoid having children w disease and identify people at High risk for conditions that may be treatable.
What are the problems with widespread screening?
Many people believe it is an invasion of privacy, defective alleles found in prenatal tests may increase abortions, individuals with defects have higher insurance premiums.
7 uses of genetic testing.
- Carrier screening to see if an individual carries a damaging allele
- Pre-implantation diagnosis to screen IVF embryos
- Pre-natal diagnostic testing
- Newborn baby screening
- Pre-symptomatic testing for predicting adult disorders
- Confirmation of a suspected disease
- Forensic and identity testing
What are commercialised gene tests?
Targeted at healthy people to give a probability of developing conditions like heart disease colon cancer etc. And some show the bodies ability to metabolise alcohol and drugs.
7 limitations of commercialised gene tests.
- Not regulated or verified
- Only test a small number of genes
- Lab errors
- Difficult to determine positive result cause some disease might not show eg dependent on genes and environment
- May be no treatment
- Anxiety
- Risk of discrimination and social stigmatisation
What is gene therapy?
A technique where a defective allele is replaced with one from a cloned healthy individual, providing a treatment or cure. The main challenge is developing a gene delivery system so it is inserted and functions correctly.
How does gene therapy introduce DNA to target cells?
- A virus as a vector
- A plasmid as a vector
- Injection of naked plasmid DNA.
What is somatic cell therapy?
Targets body cells in the affected tissues. May be therapeutic but changes not inherited by daughter cells so doesn’t appear in future gens.
What is germ line therapy?
Introduces corrective genes into germ line cells eg oocyte so the genetic correction is inherited. This is controversial. Genes interact w the way other so this has unpredictable affects.
How is DMD caused?
The ribosome meets a stop codon too early so the dystrophin protein isn’t produced so people with DMD suffer muscle loss.
How does the drug drisapersin work for people with DMD?
Antisense oligonucelotide (50 nucleotide sequence complimentary to mutated sequences). Binds to MRNA over the exon with deletion acting as a molecular patch.
What does drisapersin do?
That portion of RNA becomes double stranded where the exon with deletion is so the ribosome can’t translate it. This restores the reading frame so that a shorter partially functioning dystrophin can be synthesised. It’s called exon shipping.
How is gene therapy a treatment for DMD?
A shortened version of the healthy gene designed because normal version too long to put in a virus.
What is the genotype like for people with CF?
Homozygous for an autosomal recessive allele. The normal allele codes for CFTR.
What is CFTR?
a cell membrane protein called cystic fibrosis trans-membrane regulator. It transports chloride ions our of cells and then sodium ions and water follow which causes mucus to be watery.
