7. CF treatment and testing

Question 1

How are liposomes used in gene therapy?

Answer 1

1. A copy of the normal allele is inserted into a plasmid
2. The plasmids are then combined with liposomes to form a liposome DNA complex
3. The liposomes then combine with the cell membrane (as they are phospholipids) and carry the DNA into the cell
4. The normal allele is incorporated into the genome and transcribed
5. The mRNA is translated and a functioning CFTR protein produced

Question 2

How are viruses used as vectors in gene therapy?

Answer 2

1. A virus that will target desired tissue is selected
2. The DNA sequence that codes for replication is removed from the virus and replaced with the normal allele
3. A promoter sequence thast initiates transcription and translation is also added
4. Virus infects target cell and it’s viral DNA remains independent within the nucleus of our cells
5. Normal allele is incorporated into the genome where it is transcribed and translated
6. A functioning protein is produced in the target cells

Question 3

How does gene therapy prevent/ cure some genetic disorders?

Answer 3

Normal allele is incorporated into the genotype so when it is transcribed and translated the protein produced functions normally

Question 4

Why is gene therapy only permitted in somatic cells and not germ cells/

Answer 4

If something were to go wrong in germ line treatment it could effect future generation

Question 5

What are the benefits of gene therapy?

Answer 5

Potential to prevent and cure genetic disorders
Treat a variety of disorders
Trials can result in effective treatments being produced

Question 6

What are the risks/isuues of gene therapy?

Answer 6

Viruses could mutate and cause another disease
Inserted genes may disrupt existing base sequence causing further problems
long term effects of new techniques not known
Effects are only temporary as cells are replaced
Difficult to target large areas of body with just somatic therapy

Question 7

What can genetic screening be used for?

Answer 7

confirming diagnosis
Identifying carriers
Testing embryos

Question 8

Why must a negative result for CF be treated with caution?

Answer 8

there are so many mutations that cause the disorder so not all mutations can be tested for

Question 9

How does amniocentesis test for CF?

Answer 9

Needle inserted into amniotic fluid to collect cells from the foetus which can then be tested for the faulty gene.
15-17 weeks
0.5%-1% miscarriage risk

Question 10

How does chorionic villus sampling test for CF?

Answer 10

Sample of placental tissue removed through wall of abdomen and can be tested for faulty gene.
8-12 weeks
1%-2% miscarriage risk

Question 11

How is PIGD used to test for CF?

Answer 11

When carrying out IVF a cell can be removed from the embryo before implantaion. The DNA can then be analysed.
It can be unreliable to removes the need for an abortion

Question 12

In studies, when treating someone why are the treated children/ people compared with their untreated siblings?

Answer 12

To show if the treatment were effective

control over environmental factors