UK GCSE level age ~14-16, ~US grades 9-10 Biology revision notes re-edit 12/05/2023 [SEARCH]

 Genome: 3. Genetic screening - using data from the human genome project - potential medical treatments and ethical issues and concerns

Doc Brown's Biology exam study revision notes

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There are various sections to work through, after 1 they can be read and studied in any order.

INDEX of biology notes on the human genome

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(3) Genetic screening - using data from the human genome project, potential medical treatments, issues

Introduction

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 fetus (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 fetus 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.

Even using embryos in research projects is considered to be unethical.

(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!


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