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KEY
STAGE 3
WHAT IS THALASSAEMIA- A GENERAL OVERVIEW 1. Thalassaemia is a serious autosomal recessive genetic blood disorder. You cannot catch it or develop it. It is inherited as carrier form or as Thalasssaemia Major. One form cannot change into another. 2. The Carrier has inherited just one Thalassaemia Gene from either parent. A Thalassaemia Major baby inherits two Thalasssaemia genes- one from each parent. Both parents must be carriers in order to have a Thalassaemia Major child. 3. Carriers are perfectly healthy. The “haemoglobin electrophoresis” blood test can reveal a carrier. 4. If both partners are carriers, there is a 25% chance at each pregnancy that the child will inherit both their Thalassaemic genes and have Thalassaemia Major. This is a Mendelian inheritance pattern. 5. A child with Thalassaemia Major is unable to make enough blood cells and develops a severe life threatening anaemia. If this child is not transfused with blood he/she could die in childhood. 80% of Thalassaemia Major births in the UK occur in Asian families. 6. Besides blood transfusions every month, this child requires daily iron removing treatment that involves 8-12 hours of a pump driven continuos injection. This is done at home. 7. There is no effective cure for Thalassaemia Major. The blood transfusions and the treatment are life long. 8. Thalassaemia Major can be prevented. A simple blood test done by your GP will reveal if you are a Carrier. You get yourself tested first. If you are a carrier then get your partner tested. If your partner is not a carrier you have nothing to worry about. 9. Where both partners are carriers, you can still have children. There is a 25% chance at each pregnancy that the child has Thalassaemia Major. You can have the pregnancy tested and find out if the baby is affected. You then have an informed choice of continuing the pregnancy. 10. Up to 1 in 7 Asians are carriers of the Thalassaemia Gene. The Thalassaemia gene affects particularly people of Mediterranean, Asian or Middle Eastern origin. However, up to 1 in 1000 of the indigenous UK population carry it as well. 11. The incidence of Thalassaemia Major can be eventually reduced to zero by carriers making informed decisions about having children. It is vital that awareness is raised about the disorder. TEACHERS NOTES Why do teachers need to know about Thalassaemia? 1) Teachers are in a position to raise awareness among young people about Thalassaemia and contribute to its eradication. 2) Teachers can counsel and reassure young people who are anxious about the condition. 3) Teachers can support young people with Thalassaemia in school. 4) Teachers can raise general awareness about blood disorders which affect the diverse communities of Britain. What can teachers do? 1) Teachers can raise awareness of Thalassaemia by targeting the condition in assemblies and tutor group sessions. 2) Teachers can include Thalasssaemia as a topic in their lesson. How can Thalassaemia be included in lessons? 1) Teachers of PHSE ( Personal, Social and health Education) and Science can include Thalassaemia in their scheme of work. 2) PSHE courses feature Moral views of relationships and Parenthood and Family are topics for discussion and reflection in Key stage 3 and 4. Young people informed about the nature of Thalassaemia, can come to understand the importance of preconception blood tests. 3) In Science Key Stages 3 and 4, Thalassaemia can be introduced, described and used as an example of an inherited disease in the same way that Sickle cell anaemia is currently used as example. 4) National curriculum requirements in Science Key Stage 3 and 4 present opportunities to consider Thalassaemia that part of the Programme of study entitled Life Processes and Living things, where pupils will learn about human biology, including reproduction and health and will learn about inherited causes of variations under Variations, classifications and inheritance. The programmes of study for Key Stage 4 Single and Double Science requires that students be taught that some diseases can be inherited. It is also required that students be taught the mechanism of monohybrid inheritance where there are dominant and recessive alleles. 6) For Key Stage 3 and for students studying either Single and Double Science the programme of study requires that they be given opportunities to “use scientific knowledge and understanding to evaluate the effects of some applications science on health and on quality of life” ( DfEE Science in the National Curriculum. Programme of Study 2, Application of Science) 7) While Sickle Cell Anaemia is the best known example of a genetic mutation altering blood cell function, being a carrier of Thalassaemia is the most common human genetic condition. The question of why this should be can be raised during work on Genetics, Inheritance and Evolution ( Science Key Stage 4, Life processes and Living Things) and students are encouraged to consider why Thalassaemia carriers are most common in areas of the World where Malaria persists- the Natural selection process which occurred because the b Thalassaemia mutation affords some protection to carriers against malaria is a good topic to discuss. 8) Why Thalassaemia is now a vital Public health issue in countries such as the UK, being outside the traditional high Malaria Areas, is a question which can be linked to Geography Key Stage 3 and Key Stage 4 work where the cause and effects of migrations are studied. ( National Curriculum Geography, Key Stage 3, Programme of Study: Thematic Studies- Populations) CURRICULUM REFERENCES The message to the teachers is clear: the existing curriculum allows for Thalassaemia to be taught as an example of an inherited disorder. Teaching about Thalassaemia will hugely increase the chances of its eradication. 1) PSHE: Moral Views of Relationships and Parenthood and Family are topics for discussion and reflection in key stage 3 and 4. 2) D fEE Science in the National Curriculum, Key Stage 3 and 4, Application of Science; Life Processes and Living Things: Variations, Classification and inheritance; Genetics, Inheritance and Evolution 3)
DfEE Geography in National Curriculum, Key Stage 3 and Key Stage 4 Thematic
Studies- population. KEY STAGE 4 GENERAL INTRODUCTION At key stage 4, Thalassaemia Genetics, Clinical Facts and the ethics of genetic tests can be explored in more detail. Thalassaemia can be covered in the Double and Single Science Programme of Study entitled Processes and Living Things, Variation, Inheritance and evolution. Teachers of PSHE at Key Stage 4 will be able to discuss the ethical implications of Genetic testing. THALASSAEMIA GENETICS 1) b Thalassaemia is a recessive gene caused blood disorder. As all recessive gene disorders, it is inherited as two forms: A person can inherit just one Thalassaemia gene and be a healthy CARRIER or inherit two Thalassaemia Genes, one from each parent, and have the full and devastating condition: Thalassaemia Major. 2) b Thalassaemia is referred to as being a single gene disorder and it is also classified as an autosomal gene disorder. The genes affected are a pair of b globin genes located on Chromosome 11. 3) These genes are responsible for the production of b globin, a complex protein that forms the haemoglobin in the red blood cells. 4) In b Thalassaemia, the individual inherits mutated genes. The manner in which these mutations occur are many. In b Thalassaemia a majority of the mutations are gene deletions. The presence of these mutated genes in certain locations or populations may have due to a slow process of natural selection. Carriers of the Thalassaemia Gene have some protection against malaria. It is likely that a parasite that causes malaria and is carried by the mosquito may have been a likely natural selecting agent or vector. This is probably why the gene predominately affects people from the Mediterranean, South Asia (Pakistan, India, Sri Lanka and Bangladesh) and areas where there is a high incidence of malaria. 5) A Carrier is an individual who has inherited only one faulty (mutated) gene. A carrier's b-globin gene pair on chromosome 11 will have one good and one faulty gene in the b globin pair ( can be from either parent). A carrier's genes will thus be producing reduced quantities of b globin and his/her red blood cells will be smaller on account of reduced haemoglobin being produced. 6) A Carrier can pass on their faulty genes to their child. If both partners are Carriers then there is a 25% chance at each pregnancy that their child could inherit two faulty genes, one inherited from each parent, and have the devastating full blown condition: Thalassaemia Major. This child will have no b-globins and thus have poor and unsustainable red blood cells. 7) You cannot “catch” Thalassaemia. You must inherit it. A Carrier will not develop Thalassaemia Major. b (Beta) THALASSAEMIA CARRIER- CLINICAL FACTS 8) Human blood is made up of red blood cells that carry oxygen from the lungs to all parts of the body, white blood cells that fight infection, platelets that help seal up wounds and repair tissue. Blood also has other dissolved minerals and substances. Both the blood cells and others substance are all held in a yellow liquid called the blood plasma. 9) Thalassaemia affects red blood cells. A red blood cell is full of haemoglobin. This is an iron rich complex protein that binds with oxygen and gives blood its rich red colour. Haemoglobin is made of Haem and the globins. Haem is a complex mixture of iron and protoporphyrin and the Globins are two complex proteins called a Globins and b Globins that link up with haem to give you haemoglobin. 10) In a Carrier there will be less b Globins made as they only have one good gene. Less b Globins mean less haemoglobin made. This individual’s red blood cells are smaller on account of the fact that less haemoglobin is packed into the red blood cell. However, this individual is healthy and will not be aware of the condition. Only a simple blood test arranged by the GP can reveal a Carrier. b(Beta)Thalassaemia carriers are easily discovered by a Haemoglobin electrophoresis test on a sample of blood. 11) In sharp contrast to their healthy Thalassaemia carrier parents, children with Thalassaemia Major have two faulty genes. They have no genes there to produce b globins. Their red blood cells will be formed poorly and they will have unsustainable adult haemoglobin. 12) These children will develop severe anaemia that is diagnosed as early as 2-6 months of age as the child's red blood cells will be poorly formed and are destroyed very rapidly. This child needs monthly blood transfusions and if not transfused they could die by age 2. Their is no effective cure and the treatment is life long and full of complications. 13) Because this child is unable to make their own haemoglobin, the additional blood they are getting in transfusions is destroyed without recycling of the iron into new red blood cells. This iron is retained by the body and a child with Thalassaemia Major faces long term ill health due to this iron overload. If this iron is not removed, the iron damages the organs and hormone systems/glands and the child dies by 20 years. Iron overload is a common cause of ill health and early death. The iron removing therapy requires daily injections. The treatment is given at home through a daily twelve hour continuous injections of a drug called Desferal delivered slowly via a syringe driver. In young children this is a painful and tiresome routine that the parents undertake every night. A Thalassaemia Major patient is constantly at risk of chronic illness related to excess retention of iron which can result in liver disease, diabetes, delayed puberty, stunted growth and other hormonal deficiencies. Early death is common place due to heart failure after complications due to non-compliance to treatment. 14)
The psychological impact on a Thalassaemia Patient and his/her family
can be devastating and it affects compliance. Early death due to non-compliance
because of psychological fatigue is common place. Discrimination at
school and from employers, obtaining and retaining employment and other
career complications are encountered. The treatment costs the State
up to an estimated £1 million to raise a child 15) Financial penalties such as difficulties in obtaining mortgages, insurance cover and general loans can also place an enormous stress on the patient. Students can discuss this in light of their own career prospects and what this would mean to them. 16) b Thalassaemia can be tested, predicted and prevented. There are many ethical issues involved in this area. We will only cover the Science of the tests. The School or class can develop this further. The film GATTACA is recommended to all students as it covers many ethical issues. We can test the carriers by a simple blood test called the haemoglobin electrophoresis. This is not a DNA test and is very easy and cheaper than DNA test. In the UK the GP should be able to carry out this test for you free. We can also test the developing baby, foetus, in the womb to see if it has Thalassaemia Major. These tests are DNA based tests. ETHICS AND GENETIC TESTS 1) Because b Thalassaemia is a recessive gene disorder, you need both parents to be carriers in order for them to have a child with Thalassaemia Major. As all recessive gene disorders, we have a Mendelian inheritance pattern. There is a 25% chance at each pregnancy that a couple where both partners are carriers could have a child with Thalassaemia Major. This means that they could still have children who are healthy. 2) It is the Mendelian Chance that in each pregnancy there is a 75% chance that the child is healthy. That is 25% chance that the child has no Thalassaemia genes, 50% chance that they have only one gene and are carriers like their parents and 25% chance that they have both genes and have the full condition. 3) Whether a couple chooses to test or not is a deeply personal matter. Many opinions will be expressed at a social and community level. The students are encouraged to find these out. 4) However, the choice to test the foetus is ideally first mentioned to an individual when he or she first goes for his/her own test to determine if they are carriers. This is usually part of the genetic counselling exercise where an individual is found to be a carrier. 5) However, where both partners are found to be carriers, the couple should ideally be informed about testing the foetus before they plan a family. A proper Genetic counselling exercise for the couple and even the whole family is an appropriate time to mention this. 6) The opportunity to test the foetus is first formally offered very early in a pregnancy. It is only offered to a couple when BOTH partners have been found to be Carriers and they both CHOOSE to test the foetus and exercise an informed choice after considerable genetic counselling. The school can work on issues relating to cases where one partner may not agree to test whilst the other may. Or where the couple may choose to test and the family may oppose. The Medical Research Council, Research Update 15, Ethics and the Gene Map, comments: “Ethics is an intellectually respectable discipline but it is not like mathematics where there are typically definite right or wrong answers. What ethics can help people to do is to think clearly and rationally about the moral questions”. THE TESTS 1)
There are 3 tests available. Although each test has its respective merits
and has to be done at its own optimum time, CVS is the most commonly
offered test. These tests are different from the blood test, the haemoglobin
electrophoresis, used to determine a Carrier. There are three
tests available. The Chorionic Villus Sampling (CVS) Test is done from
10 weeks of pregnancy, Fetal blood sampling from 18 weeks and the rarely
done Amniocentesis is between 14-18 weeks. 2) The choice of which test to use is a very carefully considered matter. However, if the mother has presented herself early in a pregnancy, Chorionic Villus Sampling is the best test because of the ease of doing it and its acceptability to the mother as it can be done earlier in the pregnancy. 3) Chorionic Villus Sampling (CVS) test involves taking a small sample of the developing placenta from 10 weeks of pregnancy. The placenta, which is attached to the growing foetus by the umbilical cord, contains the DNA imprint of the baby. The placenta and its position is first assessed by ultra sound. A sample of the placenta is obtained either through the vagina or through the abdomen dependent upon where the placenta is located. The sample of placenta has its DNA then tested to see if the child's Haemoglobin making genes are affected and this determines if the baby has the full blown condition Thalassaemia Major. 4) Fetal blood sampling involves test the taking of a blood sample from the umbilical cord of the foetus in the womb. Fetal blood sampling is used when the foetus has developed more and the pregnancy has advanced to 18-22 weeks. An affected baby will have little or no adult Haemoglobin HbA. This test is used when the CVS test cannot get access to the placenta or when the DNA test cannot determine the exact DNA profile of the baby. 5) Amniocentesis involves taking a small sample of the amniotic fluid that surrounds the baby. As there are very few cells from the baby floating about in the amniotic fluid, the test requires culturing and growing of the captured cells in the laboratory and then the DNA of these cells is tested as per the placenta test. 6) EASE OF SAMPLING AND TESTING: The CVS has merits as you can take a sample from a sizeable placenta and have a DNA test made available within 5- 10 days. Fetal blood sampling requires getting access to the small umbilical cord and then measuring the Hb A or DNA- it can be difficult. Amniocentesis requires a cumbersome process as it requires looking for fetal cells in the amniotic fluid and then the culturing of the cells in addition to the DNA test. 7) PSYCHOLOGICAL ASPECTS OF TESTING: It is reported that the earlier a test is done in a pregnancy, the lesser the psychological factors affecting the mother and couple. CVS is done from 10 weeks and is very early in the pregnancy and the mother has not developed a deep bond with the pregnancy- especially when it is not showing and/ or has not been physically demanding. Fetal blood sampling is quite late and will be more demanding psychologically where termination of a pregnancy is a considered option. 8) SAFETY AND ACCURACY: CVS and fetal blood sampling has a reported miscarriage rate of 1 in 100 (1%) tests. Amniocentesis has a 1 in 200 miscarriage rate. 9)
ETHICS OF TESTING: The following comments from Professor Marcus Pembrey
in the Progress Guide to Genetics (Progress Educational Trust) are appropriate
to bear in mind: “The technical aspects of the testing process are getting
simpler year by year, but this does not mean the decisions that people
have to make are easier. Testing must be linked to adequate counselling,
exploring what they would feel and how they would cope if they tested
positive” THALASSAEMIA
AND THE PUBLIC HEALTH Genetic disorders like Thalassaemia Major will become a major policy issue during the next century. Genetic disorders will begin to have a disproportionate impact upon the State when their treatment and management is compared to that of the traditional illness and epidemics. Preventative education and vaccination has removed the spectre of many illness from our communities. Advances in sanitation and Public health infrastructure have reduced the incidence of the major killers that plagued our ancestors. Genetic disorders have no cures. Treatments for genetic disorders are life long, involve painful protocols, absorb expensive and rare drugs, require constant monitoring and control, need disproportionate time from the consultants, rotate around the near full-time involvement of the nurses, counsellors and other socio-psychological professionals. The impact upon the State's health, social welfare, education and overall economic system is enormous. It takes £1 million to raise a Thalassaemia Major child to Adulthood (30 yrs). The impact upon the individual and his/her family is immeasurable. The physical effects of the condition, the side effects of the treatment and the caprice of sexual development and growth can place an enormous psychological burden upon the individual. Social stigmatization of the sufferers, the perceived shame of the parents and the general helplessness can reduce the individual’s self esteem and force them into isolation. At a tangible and measurable level, discrimination by employers, mortgage and insurance companies place extreme stress upon the individual. Glossary Most of the terms and terminology of genetics can be found in good Genetic text books and dictionaries. We provide a few useful terms that relate to Thalassaemia in this section Autosome/
Autosomal genes: These are genes located on chromosomes other than
the gender pair chromosome number 23. The conditions linked with autosomal
genes affect both genders equally. Boys as Dominant genes: The genes function differently to the recessive genes. In order for you to develop the full condition you need only one gene. The individual who carries this gene develops the full condition. Some common Dominant gene caused conditions are Huntington’s neurological disorder and Adult polycystic kidney disease. Haemoglobin electrophoresis test: This a test that takes a sample of your blood and tests your haemoglobin types. It is a very reliable way of determining if you are a carrier. This is not a DNA test. Genes: Genes are the building blocks of life. They are responsible for making all the proteins that the body needs to build muscles, bones, hormones and blood. We inherit our genetic blue print on approximately 100,000 pairs of genes. The DNA of the genes holds the code for all the human body. The 2 pairs (4 in number) of a(alpha) genes on chromosome 16 and 2 b (beta) genes on chromosome 11 are responsible for making the proteins needed for haemoglobin in the red blood cell. Mendelian inheritance: Named after Gregor Mendel a Swiss Monk who discovered that in pea plants some genes are dominant and some recessive. In recessive genes he discovered that in order for them to express themselves they need two copies one from each parent. In dominant genes you need only one. He, however, discovered another important fact that if both parent plants were carrying a particular recessive gene, then there was a probability that 50% of the offspring plants would carry the gene like the parents, 25% of offspring plants will not inherit that gene and 25% offspring plants will inherit both the genes and the gene will then express itself: e.g. red flowers in offspring from two pink flowered parents. This inheritance pattern has a big implication on testing, screening and prevention when managing public health programmes in recessive gene disorders. Recessive genes : Recessive genes work in pairs. This means that in order for someone to develop a recessive gene related genetic condition. That individual must inherit two faulty genes: One from each parent. Mendelian inheritance patterns of inheritance occur. There is a 25% chance at each pregnancy that the child will have the full blown condition. A Thalassaemia Carrier has one Thalassaemia Gene and so does not suffer the full blown condition. Tests for carriers: Genetic science has given us the ability to test an individual for many conditions. In Thalassaemia we do not need a DNA test to identify the Carrier. We use the Haemoglobin electrophoresis test that takes a sample of your blood and tests your haemoglobin types. It is a very reliable way of determining if you are a carrier. In other genetic disorders we must use a DNA test. A small sample of the individuals tissue or body sample is taken and a DNA test applied. The individual will reveal mutations on the genes we are looking for. Tests for pregnancies: These are DNA tests that are performed on tissue samples taken from the foetus or on foetal cells floating in the amniotic fluid. In Thalassaemia the chorionic villius sampling test involves taking samples of the placenta, the big tissue that attaches the baby to the mothers womb, and then doing DNA tests on it. This is a reliable test and can be done as early as 10-12 weeks of pregnancy. FURTHER
WEBSITES AND RESOURCES WEBSITES www.ukts.org This is the website for the UK Thalassaemia Society and has many interesting facts and events listed. The UK Thalassaemia Society was established in 1976 and has been in Thalassaemia health education field for over 20 years. Other Web sites You can use any search engine and search the web using : Thalassaemia or Thalassaemia (Different spelling). There are many interesting Web sites across the World. We have American, Indian, Malaysian, Australian and other sites which give a range of views and experiences of various communities World wide. PUBLICATIONS UK
THALASSAEMIA SOCIETY- PUBLICATION LIST ON WEB PAGE OTHER PUBLICATIONS Progress
guide to genetics Science
File 2- An introduction to Genetics Applications
of Genetic- Gregory .J. (1995) MRC
Research update 15 Ethics and the gene Map Genes
and you Science
parks and museums.
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