- Helps us to understand how disease is inherited and the chance so children being carriers or victims of the disease
- Explain available tests
- Explains possible courses of action to take place after test results/outcome
1.RIGHTS + DUTIES
2.MAXIMISING THE AMOUNT OF GOOD IN THE WORLD
3.MAKING OWN DECISIONS
4.LEADING A VIRTUOUS LIFE
What is genetic testing?
Genetic testing is the use of laboratory tests to determine the genetic status of individuals already suspected to be at high risk for a particular genetic disorder based on family history or a positive screening test.
What is genetic screening?
Genetic screening is tile use of simple diagnostic tests performed on a large number of individuals to identify those who are at a high risk of having or passing on a specific genetic disorder.
What is the difference between genetic testing and genetic screening?
Genetic testing and screening are similar in that both involve the use of laboratory tests to reveal the presence of disease-causing genes. Although genetic screening and testing are essentially the same since they both involve the same medical procedures, the major difference between them can be explained in examining WHY an individual undergoes laboratory testing.
What is done in a gene test?
In gene tests, scientists scan a patient’s DNA sample for mutated sequences. A DNA sample can be obtained from any tissue, including blood. For some types of gene tests, researchers design short pieces of DNA called probes, whose sequences are complementary to the mutated sequences. These probes will seek their complement among the three billion base pairs of an individual’s genome. If the mutated sequence is present in the patient’s genome, the probe will bind to it and flag the mutation. Another type of DNA testing involves comparing the sequence of DNA bases in a patient’s gene to a normal version of the gene.
Who can benefit from genetic testing and screening?
Key Points on Genetic Testing
What screening tests are available?
TYPES OF GENETIC TESTING
PROS & CONS of Genetic Testing
Ethical Issues: (Germ line therapy is illegal due to these reasons)
Gene therapy involves inserting copies of a normal allele into the chromosomes of an individual who carries a faulty allele. If a mutated gene causes a necessary protein to be faulty or missing, gene therapy may be able to introduce a normal copy of the gene to restore the function of the protein.
However, it is not always successful, and research is continuing.
It is illegal to do this to sex cells (Germ Line Therapy), because any (bad) changes would be inherited by the individual’s offspring. Instead, gene therapy is used on somatic (body) cells. This means that the individual could pass on their faulty allele to their children, even if they get better themselves L
A gene that is inserted directly into a cell usually does not function. Instead, a carrier called a vector is genetically engineered to deliver the gene. Certain viruses are often used as vectors because they can deliver the new gene by infecting the cell. The viruses are modified so they can’t cause disease when used in people. If the treatment is successful, the new gene delivered by the vector will make a functioning protein.
The basic process
Researchers are testing several approaches to gene therapy, including:
Problems in the process
Plasmid = extra loop of DNA that has been GM to contain the “correct” allele to produce the functioning protein
Liposome = spherical phospholipid bilayer that fuses with the cell membrane, whilst carrying in the GM plasmid
PROS & CONS of Gene Therapy
Ethical, religious and moral issues:
The intrusive nature of gene therapy means that we can discover information about our genetic make-up than we are meant to know. The knowledge could have a negative impact on their lives and if that knowledge was to influence any life decisions in a negative way then it is questionable whether genetic screening is morally correct.
Genetic screening can also be carried out on unborn babies – if this screening showed that a child was carrying a disease this may lead to the parents deciding to abort the child. This is clearly a very morally questionable act as many would argue that a person does not have the right to play God with another person’s life.
Similarly, a couple who are aware of their genetic make-up and know that they’re both carriers of a specific genetic disorder may decide against having children to avoid passing on the defective gene. Again, many would argue that this goes against the natural order.
Gene therapy has the potential to be misused – for instance the concept of “designer babies”, where specific genes are selected in order to create the perfect child.
So, the cons of gene therapy in terms of quantity very clearly outweigh the pros.
Sex cells only contain one allele each, so you need to find out your chances of the baby having CF through punnett squares. You can trace family history through pedigree diagrams.
Monohybrid inheritance – characteristics are controlled by one gene
However, many genes usually control a specific characteristic
Caused by recessive allele – thalassaemia, albinism, phenylketonuria, sickly cell anaemia
Caused by dominant allele – Huntington’s, achondroplasia
There are many environmental factors (e.g. UV radiation) that could cause gene mutations but it can also be inherited.
When the DNA is being built an incorrect base may slip into place which could cause a mutation in the gene. If this mutation occurs in the reproductive organs, the DNA will be replicated in the sperm / egg cell and so the fertilized zygote will have the mutated gene in every cell.
Any mutations that occur in sections of DNA that don’t play a role in protein synthesis have no affect on the organism.
Sickle Cell Anaemia
Chromosome 7 carries the code to make the CFTR protein.
Why is it caused?
ATP energy is unable to bind to the ATP binding site thus the chloride ion channel cannot open and let the chloride through. The concentration gradient alters the electric gradient, which in term affects the net flow of water via osmosis. The water is drawn out from the mucus to maintain equilibrium, and so the mucus is more dry and sticky. It is able to trap more bacteria and dust hence cystic fibrosis is the result.
Most common way it’s caused (DF508):
Meselson and Stahl Experiment – Density Centrifugation Gradient
The genetic information stored in DNA is transcribed into mRNA and then transformed into protein.
The unused strand is named the Antisense / coding strand – b/c it has the same coding as the mRNA
Translation takes place on the ribosome’s in the cytoplasm – the ribosome’s are the sites of protein synthesis