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Should we screen embryos for genetic diseases?

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    In this coursework I will be looking to see if it is right or wrong for parents-to-be to have their embryos screened for genetic diseases. Screening for genetic diseases allows couples to see if their unborn baby would suffer from any disorder that runs in the family. There are over 4,000 genetic diseases around to today and over 5 million people are affected each year.

    There are many people whose opinion is that by choosing how your baby will be is a form of Eugenics.Sometimes screening embryos can help people make decisions about their future and how their life may change. Using this method can also help save people lives. But genetic screening is also causing problems such as the thinning of the gene pool and removing genes that may be beneficial in some unknown future.

    DNADeoxyribonucleic acid, or DNA for short, is a long thin chemical which contains genetic instructions for the development and functions of living organisms. DNA is made up of two strands twisted together to made something called a ‘double helix’. The helix is held together by hydrogen bonds between the bases and the strands. The part of DNA that has the genetic code for making a particular protein is called a gene.

    Genes can be found along thread like structures called Chromosomes. These are the packaging system of our DNA that allows 2m to fit in the nucleus of every cell. In the case of humans we have 46 distinct packages, 23 from each parent.GenesGenes are an area of the DNA encoding information that can be used in the production of protein.

    Humans have 30,000 or so areas of coding DNA. This DNA encodes for all of the different proteins that perform all the cellular tasks in the body and also define the different traits and characteristics we all have. One example of people traits is hair colour which is inherited from parents.Genes make such protein as;* Structural proteins where are found in muscles and hair* Enzymes such as proteases and carbohydrates.

    * HaemoglobinFigure 1; the location and storage of DNA in the Nucleus of a cell.AllelesA number of the same genes are called alleles. From this you inherit one allele for each gene from your father and one allele from each gene from your mother, making all of your non-sex cells diploid. For example, the gene for eye colour has alleles for blue eye colour and alleles for brown eye colour.

    Your eye colour will depend on the combination of alleles you have inherited from your parents.Figure 2; Diploid Inheritance of Genes.Inheriting Disease:Many diseases can be inherited throughout the family, but some are affected by their environment. These could include:* Climate* Diet* Physical accidents* Culture* Lifestyle.

    The best way to show this is by describing the lifestyle of identical twins. For example if one twin exercised regular and ate health then they would have better way of life than one who does not.What is a genetic disease/disorder?A genetic disease/disorder is a condition caused by mutations in genes or chromosomes. While some diseases, such as cancer or Alzheimer’s, are due to genetic mutations acquired in a few cells during life, the term “genetic disease” most commonly refers to diseases present in all cells of the body from conception.

    Two examples of inherited disorders are Cystic fibrosis and Huntingdon’s diseases are;Cystic fibrosis is a disorder that affects the lungs and wind pipe producing thick, sticky white mucus making it hard to breathe. Due to this it makes it hard to fight infections and simple illnesses like the common cold. CF is caused by a recessive allele in the body. To inherit CF you must have two copies of the faulty gene.

    If you only have one copy in your genes this means that you are a carrier and could pass it onto your offspring if met by another gene with the same fault. If two faulty genes are inherited there is a one in four chance that that individual’s child may inherit the disorder.The diagram shows who will get the CF disorder is each parent carries one faulty allele.Figure 3; shows who will be affected from the faulty alleleHuntington’s disorder is a disorder passed on from birth but the symptoms are not seen until middle age, which means that the disorder can’t be caught.

    The first symptom of the disorder is not being able to control the mussels; they soon find it hard to remember and finally after a few years the patient can’t control their movement. Huntington’s is caused by a dominate allele because of this unlike Cystic fibrosis you don’t need two affected alleles.The diagram shows what would happen it one of the parent had the dominate allele. In this case it is the mother that has the effected allele.

    This means that there is a 1:2 or 50% chance that any of their children may get the Huntington’s disorder.Figure 4; shows who will be affected by Huntington’s diseaseSickle CellSickle cell is a genetic disease that is caused by the red blood cells changing to a sickle shape. This happens when the proteins inside the cell stick together. Due to this the red blood cells membrane becomes stuck in the blood vessel walls.

    When the cells stick into the blood vessel’s tissue is deprived of oxygen causing ‘Ischemia’ and ‘Infraction’. This finally leads to such condition as stroke. Most of the people that get sickle cell come from parts of the world such as South-Africa, where malaria is or was very common.Figure 5; this shows what normal blood cells and sickle cells looks like and how they both affect the bodyMultifactorial and polygenic disorders:Some genetic diseases maybe also be complex, Multifactorial and polygenic.

    This means that they could be affected by multiple genes in combination with lifestyle and environmental factors. An example for multifactor diseases includes heart disease and diabetes. Even though these diseases can be in some families they don’t always have a clean-cut inheritance. Doctors can’t yet tell if diseases can be passed on to future generations or be inherited.

    These types of diseases are unfortunate and very distressing for the parent and the child affected this are why so many people want to get rid o’them. They do this by using different types of procedures to take away the faulty gene or to see whether or not they want to keep the baby. One of these procedures includes PGD.PGDPGD stands for Pre-implantation Genetic Diagnosis and is one way of screening embryos.

    Currently there are two ways in which PGD can be performed. These two procedures included, Polar Body Biopsy and Embryo Biopsy (aka Blastomere Biopsy).Polar Body Biopsy – this screening is performed after the egg has been fertilised and splits into two small cells. One of these cells doesn’t help with the growth of the foetus and slowly brakes down.

    This cell is called Polar Body and allows the doctors to take chromosomes away without harming the baby. The only problem for using the Polar Body Biopsy is that the test can only detect disorders that come from the mother and not the father.Embryo Biopsy or Blastomere Biopsy – this screening is performed on the third day of fertilisation. To screen the embryo doctors make a small incision and takes one of the dividing cell away to analyzed.

    Advantages for PGD* PGD prevents abortion of the fetuses: normally over 35% of women aged 35 or over have a miscarriage. After the PGD studies showed that pregnancy dropped from 25% to just 9%* Increased Implantation Rate.* Parents that how they are a carrier of a certain disease may decide to take the test to prevent their child from living with the disorder.* Embryos can be picked to help cure children with genetic diseases by using stem cells donated from the babies umbilical cord* Reduction in the number of children born with AneuploidyDisadvantages for PGD* Parents may not use PGD to help find genetic disease but instead to pick the gender of their child.

    * PGD costs a lot of money* Parents may pick what traits they want their children to be born with* Some people and religion’s believe that life begins after conception and shouldn’t be tampered with after this stageStem cellsStem cells are unspecialized cells, which can grow into any type of cell in the human body. These cells are used to help people who suffer with certain genetic or inherited disorders. For example doctors can grow new brain cells to help treat people with Parkinson’s disease. But these cells can only be used when people genes match the genes that are in the stem cell so that the patient’s body doesn’t reject the treatment.

    Stem cells are taken for the embryo after only a few days of being fertilized. For research doctors use embryos that are left over from fertility treatment.Figure 6; the diagram shows how stem cells are usedCase study one: Zain HashmiIn the early months of 2002 Zain Hashmi was diagnosed with a serious inherited blood disorder. To correct the problem he needed to have a bone marrow transplant to allow his body to make the correct blood-making cells.

    For the procedure to work this family need to find donor tissue that was a good match so that it wasn’t rejected by his body. Unfortunately for Zain no match was found and the only way for him to get the transplant now was by having a brother or sister that had matching tissue type. This would work by taking blood from the babies’ umbilical cord and for it to be used to make the cells Zain needs.If Zains parents got the permission to use PGD it would allow them to select embryos which didn’t carry the blood disorder.

    Luckily for the family the HFEA already allows PGD to be used for disease. But as Zain needs a certain tissue type the embryos also need to be tested for them to match. No one has asked to use PGD in this way before. Luckily HFEA agreed.

    By December of 2002 an anti-abortion group took the Hashmi case to High Court. The reason why the Hushmi’s were taken to court was because the anti-abortion group believed that no embryos should be used for the benefit of other humans. As a result of the case judges made a verdict that using PGD to select the correct tissue type for their son was against current laws and any changes had to be made in Parliament.Figure 6; a picture of the Hushmi’s family that need PGD to help save their little boys lifeOver the next four months the HFEA appealed against the High Court’s decision and won their case.

    As a result of this the Hashmi’s were allowed to use PGD and now hope that a new brother or sister may help save Zain’s life.Gene therapySome diseases can be corrected by gene therapy. This type of therapy works by replacing the faulty allele with a normal allele which is inserted into the chromosomes of an individual.Figure 7; the diagram shows how Gene therapy worksThere are four main types of viruses used as gene therapy vectors;* Retroviruses – A class of viruses that can create double-stranded DNA copies.

    These copies of its genome can be integrated into the chromosomes of host cells. For example Human immunodeficiency virus (HIV) is a retrovirus.* Adenoviruses – A class of viruses with double-stranded DNA genomes that cause respiratory, intestinal, and eye infections in humans. For example the common cold is an adenovirus.

    Figure 8; shows gene therapy using and adenoviruses victor* Adeno-associated viruses – A class of small, single-stranded DNA viruses that can insert their genetic material at a specific site on chromosome 19.* Herpes simplex viruses – A class of double-stranded DNA viruses that infect a particular cell type. (Neurons) for example Herpes simplex virus type 1 is a common human pathogen that causes cold sores.Today’s laws only allow us to use gene therapy on body cells and not sex cells.

    This is because any changes to the sex cells would be inherited by the individuals’ offspring, whereas on body cells the individual could pass on their faulty allele. Even though the therapy may cure the individual there are still chances that the disease may still affect the body. Whilst in the process of gene therapy there are many problems that could ochre;* The alleles may not go into every target cell that is affected* The alleles may join with the chromosomes in random places, so they do not function properly* Treated cells may be replaced naturally by the patient’s own untreated cellsCase study two: New embryo test to screen for 6,000 diseasesIn 2006 British fertility specialist found a new way of testing for genetic diseases. People have called the new find a ‘Big advance’ as it has boosted the test performed from 200 to nearly 6000.

    An article from the guardian stated:’It will allow doctors to test for the first time a vast array of inherited diseases for which the specific genetic mutation is not known, such as Duchene’s muscular dystrophy (DMD) and some forms of cystic fibrosis.’The article then went on to say that Guy’s team applied to the Human Fertilization Embryology Authority so they could test for other genetic diseases. One disease that applies to this fragile X- syndrome, the disease affects 1 in 8000 and 1 in 4000 boys.One couple that this affected was Linda Ball and her husband Steven.

    When Linda was younger she watched her older brother, Vince, died from a fatal disease called Duchene’s muscular dystrophy. The disease is inherited and that only affects boys. Linda watched her brother deteriorate due to the muscles being eaten.Linda was always told that she could be a carrier and if she had a boy he had a 25% chance of getting the disease.

    When she finally found out she was pregnant Linda and husband considered having the prenatal test. If the results came back saying she was having a boy they had the of keeping the baby or having an abortion. Due to this Linda decided against the test, she said;’I just couldn’t bring myself to have an abortion knowing there was a child growing inside me’. Linda knew that there was a 25% chance that their child may have the disorder but she still went ahead with the pregnancy.

    Her son Daniel was born five and half years ago and was diagnosed with the disorder.’Unfortunately we were in the 25%. Daniel is a wonderful little boy, he is very intelligent, cheeky and I wouldn’t swap him for anyone. But I do blame myself sometimes for passing on this terrible disease.

    ‘Linda then went on to say;’There is nothing worse than knowing you are going to watch your own child die.’EthicsOne medical issue that affects some couples is genetic screening. When first looking at the screening it seems like the best decision for all couples that need to use the treatment but it doesn’t always mean it is the right one. There are many ethical questions that the patients need to consider before going through with the procedure.

    * Who should know the test results?* What effects could the test results have on people’s future decisions?* Should people be made to have made to have screening, or should they be able to opt out? Is it right to interfere?More than 1 in 25 people suffer with carrying the cystic fibrosis allele. Some people feel that knowing this information is a good thing as it helps medical finding, but there are many reasons why not everybody agrees. Some people may benefit from their decision where as for others it may cause upset and much harm to the family or others that are involved.As a result of people picking whether or not they want children with certain diseases this is causing the gene pool to become thinner.

    This means that less and less babies are being born with diseases which may cause other problems such as leaving others more vulnerable to malaria. Another example from the past is the Black Death.Thousands of people died but there were people that managed to survive as they had something in their genes that fought against the virus. Due to this children that were born after the Black Death and to families that survived the virus were born with the genes that made them amine to the disease.

    People think that by choosing traits for their children it will help them in later life but it is actually affecting their future. Even though some diseases are not as common as before this is affecting the millions of people that are. As some diseases are dying out it is becoming harder for researches to find medical cures to help save patients lives.EvaluationThough out the years many people have expressed their different opinions on screening embryos.

    After looking at all my research I have come to the decision that genetic screening should be used, but only if it helps children from suffering from disorders that would affect their life in the long run. Children with Cystic Fibrous would grow up knowing they were different from the other children. They would also know that they couldn’t do certain things on their own as it may be dangerous for their health.By screening embryos for genetic diseases it would also stop the misery that could affect families from losing their child.

    Whilst looking at Zain’s story you start to see how much the family is affected by his illness. If they didn’t have any other child then they may lose the one they already grow to love and care for. People feel that creating another baby is wrong to help another person but if it saves someone you love from suffering wouldn’t it be a good idea.

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