Introduction -
analysing a person's genome!
Genetic screening is a
sophisticated type of testing involving investigating the human genome
and the results used to identify individuals who may be at increased
risk for a genetic condition or certain types of cancer, often before
the patient exhibit symptoms.
Genetic analysis can help
determine if a person is a carrier of a genetic condition, even though
they don't have the condition themselves but can pass on the genes
involved on to their children.
Genetic screening is
different from genetic testing, and is used to diagnose a specific
genetic condition when symptoms are present or if there is a strong
family history
Genetic
analysis - results of screening or testing
When you know that a particular allele causes
an inherited genetic disorder you can take action e.g.
if an allele that causes an inherited disorder
is identified, we could have regular medical checks for
these specific diseases and get early diagnosis and subsequent
treatment.
Genetic treatment might be able to cure
the disease.
From the human genome project scientists can
identify the genes and alleles that may be responsible for causing
inherited disorders, and much faster prior to the mapping of the
complete human genome.
Common diseases like cancer and heart
conditions are caused by the interaction of our genes and our
lifestyle factors.
If we know which genes predispose an
individual to certain types of disease we could be given
personal advice on diet and lifestyle (in general) to minimise
the risk of suffering from particular diseases.
However, there are many issues to with genetic
testing results e.g.
(i) From the point of view of potential
parents, there maybe crucial choices regarding whether children
may be born with a genetically inherited disorder - especially
if both parents carried the same faulty allele.
(ii) Would insurance companies be allowed
to see your 'genetic profile', are they entitled to know it e.g.
as regards health or life insurance?
More on these points below in section
(d)
Examples of using genetic testing
Example 1. A couple wishing to
start a
family might wish to know whether there is a risk of the
baby developing a genetic disorder. This another aspect of family
planning at the discretion of parents.
This can involve genetic testing at
various point e.g.
a.
Prior to conception,
parents can be tested to see if they are carriers of a defective
gene known to cause a genetic disorder.
It may be known that one of the
parents comes from a family line where a genetic disorder
has occurred.
The parents may not suffer from the
genetic disorder, but they may be a carrier of the defective
gene.
The genetic tests would show if any
parent was a carrier and the probability of the baby
inheriting the disorder - the parents can then make an 'informed
decision' as to whether to have a child.
see
Introduction to the inheritance of
characteristics and inherited disorders
b.
After conception or laboratory
fertilisation, the embryo or
foetus (embryo >8 weeks
old) can be tested - see section (ii) below on embryonic genetic
testing.
A pregnant woman can be tested by
extracting a sample of DNA from the amniotic fluid
which surrounds the foetus in the womb - there is a very
small risk of causing a miscarriage.
The tests will show whether
the
foetus's DNA is carrying any of the genetic variants linked
with a disorder.
If a positive test for such a variant
is found, the couple can then make an 'informed decision' as
to whether to terminate or continue with the pregnancy - a
very personal and agonising family planning decision.
c.
The newborn baby can be
genetically tested to show whether a genetic disorder has been
inherited allowing early intervention of medical treatment and
subsequent long-term management of the disorder.
Example 2. Using
in vitro
fertilisation (IVF) embryos are fertilised in a
laboratory and then implanted into the mother's womb.
Prior to implantation it is possible to remove
a cell from an embryo and analyse the DNA i.e, the genes and likely genotypes/phenotypes.
This allows the detection of genetic disorders
e.g. cystic fibrosis (described above) which is caused by the
presence of one or more faulty genes.
You can choose to allow a genetic
disorder free embryo to fully develop into a baby in the
mother's womb - this minimises the baby inheriting the genetic
variants linked with the disorder.
However, this ability to analyse genes in this
way leads to ethical, social and economic concerns and questions
about embryonic testing i.e. embryo screening for abnormal-undesired
genetic traits, on which crucial decisions can be made e.g.
termination of pregnancy.
e.g. after screening, embryos produced by
IVF, containing abnormal alleles can be destroyed.
Example 3.
Other points on genetic testing
Genome research data shows scientists the
common genetic variations between people, most of which are
benign and no danger to our health.
However, as I've already pointed out:
Some
genetic variations are linked to our predisposition to certain
disease - so this will help to design new drugs specifically
tailored to suit people of a particular genetic trait.
In the UK newborn babies are
routinely tested for particular genetic variants known to
cause genetic disorders e.g. the double recessive allele
that causes cystic fibrosis.
The results from genetic
screening enables the medical treatment-management
to begin promptly while the baby is still very young.
Arguments for embryonic/fetal screening and other
genetic testing
(i) It stops newborn babies suffering as they
grow up into adults.
(ii) Reducing the number of people suffering
with a genetic disorder that is costly for healthcare systems to
deal with.
(iii) Procedures like IVF, accompanied by
genetic testing, are strictly regulated and parents are not allowed
to choose desirable traits.
Parents are not allowed to choose the sex
of their child, unless it is for good medical health reasons.
(iv) Other 'positive' points on genetic
testing:
Early intervention for potentially serious
diseases has already been mentioned.
Drugs for chemotherapy in cancer treatment
are continually being developed and tested - you match a drugs
performance against a person's specific genetic profile - this
increases a 'working' database of treatment for future patients
- another positive outcome from such treatment research is the
minimising of side-effects which can quite drastic from
ant-cancer drugs.
Arguments against embryonic/fetal screening and
other genetic testing
Many objections centre around
the ethical issues of
IVF.
(i) IVF procedures often
result in unused embryos being destroyed and some people
consider this
unethical - immoral, because you have destroyed a
potential human life.
Some even using embryos in
research projects is considered to be unethical.
This is a
difficult area of moral philosophy, to which science provides
alternative actions, but cannot say which is the 'correct'
choice for a particular person!
(ii)
Terminations of IVF
pregnancies on the grounds the baby may be born with a genetic
disorder implies that the resulting children are undesirable and
prejudice increased towards them.
Would potential parents feel
under pressure NOT to have children with a potentially inherited
genetic disorder.
(iii) The genetics and genetic testing of
embryos before implantation in the mother's womb raises the
ethical issue of preferential choice of characteristics of the
baby e.g. choice of gender, eye colour irrespective of whether you allow
a child to be born with disabilities.
(iv)
Genetic screening is
expensive and the costs of gene technology treatments are
high.
The cost increases, the more
personal the treatment, because the more specialised the drugs
must be.
Surely this risks unfair
access to these expensive treatments?
In the UK NHS treatment
is free - BUT, is it locally available? Can you jump the
queue by using private medicine?
In other countries, or UK
private medicine - what does your insurance premium cover?
(v)
The accuracy of genetic
testing
Unfortunately, due to the
complexity of DNA structure, genetic testing is not 100%
accurate.
A positive test for a
faulty gene, that is incorrect, will causing stress to the
couple, and possibly the wrong decision to terminate a pregnancy
because of fear of the baby inheriting a genetic disorder
when there is actually no need to be concerned.
A negative test for a
faulty gene, that is incorrect, means the couple are
completely unprepared for the birth of a child with a
genetically inherited disorder, causing considerable stress in
their lives when the baby is born.
(vi)
Other 'negative' points on
genetic testing:
Is the use of gene technology
good in the long term, since we don't actually know what the
effects will be on future generations?
What might you think if you
know from an early age you are more susceptible (more
predisposed) to a particular disease? Won't this lead to
stress thinking about it, especially if there isn't cure for
it? Might you feel uneasy and worried if you 'seem' to
exhibit symptoms?
Would you be discriminated
against by insurance companies (e.g. insurance refusal or
increased premiums) or employers (e.g. refused long-term job
contract) if they knew you were likely to suffer from a
genetically inherited disorder.
Society must decide on a
code of conduct relating to potential discrimination AND
privacy of your medical details.
Just imagine the
problems caused if you genetic profile had to be
submitted with a job application!
Be able to describe what genetic screening of the human
genome is.
Understand the importance and controversy about collecting
genetic data, as well as recognising the data potential for developing and
selecting medical treatments.
Appreciate the ethical issues and concerns about genetic
testing.
Issues involve parental wishes and decisions e.g. concerning
an unborn baby, monitoring development of the foetus, IVF treatments, and
the accuracy of genetic data when screening an embryos for possible genetic
disorders.
Be able to make
informed judgements about the social and ethical issues concerning the use
of stem cells from embryos in medical research and treatments
Be able to make
informed judgements about the economic, social and ethical issues concerning
embryo screening.
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