76 Epidemiological studies - hicomau

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76 Epidemiological studies - hicomau ...

7.6 Epidemiological studies Further questions and answers


    Bk Ch7 S7.6 FQ1

    Find out how techniques such as amniocentesis and chorionic villus sampling are used to determine

    genetic abnormalities in the developing foetus. What is involved in each technique? Outline any risks

    associated with these procedures. List some of the conditions that can be identified using these



    Bk Ch7 S7.6 FA1

    Amniocentesis is a technique that involves the removal of foetal cells from the amniotic sac in which

    the developing foetus is contained. These cells are then examined using a microscope. This method is

    used to determine whether or not any chromosomal abnormalities are present. Down syndrome can be

    diagnosed using amniocentesis because it shows the presence of an extra number 21 chromosome. The

    sex of the foetus is also evident using this method. Amniocentesis increases the risk of miscarriage. It is

    usually performed on older women, who have an increased risk of carrying a child with Down

    syndrome. It may be performed on younger women who have been identified as having an increased

    risk of some chromosomal diseases.

    Chorionic villus sampling is a technique that removes foetal cells from the outer membrane of the sac surrounding the foetus. Cells are examined for chromosomal abnormalities such as those evident in

    Down syndrome. The advantage of this technique over amniocentesis is that it can be performed earlier

    in a pregnancy; however, there is also an increased risk of miscarriage.


    Bk Ch7 S7.6 FQ2

    At the present time, we cannot cure inherited diseases.

    a Explain why this is so.

    b Describe how genetic engineering techniques might help overcome inherited diseases in the future. c What is gene therapy? How can it be used to treat some inherited diseases? Use an example in

    your answer.


    Bk Ch7 S7.6 FA2

    a Inherited diseases are genetic in nature. With the exception of eggs and sperm every cell of an

    individual’s body has the same complete genome. This means that every single cell also contains

    the defective gene causing an inherited disease. To cure an inherited disease we need to correct

    the defective gene in all of the body cells.

    b Genetic engineering may be beneficial to couples planning a family but who have a history of a

    particular genetic disease in one or both families. Eggs and sperm may be harvested using IVF

    technology, genetically altered to correct the defect, and then allowed to unite in fertilisation

    before being implanted. Similarly, a fertilised egg that is at risk or known to have a genetic defect

    could be genetically altered before being implanted. This technique can also be applied to

    embryos at very early stages of development, usually less than the eight-cell stage. Current gene

    therapy techniques applied to an undifferentiated embryo could also be useful in correcting

    genetic defects.

    c Gene therapy is the technique of treating patients with otherwise untreatable inherited diseases

    with genetically engineered cells or modified DNA. This involves the insertion of non-defective

    genes into a target tissue of the patient with the aim of replacing defective genes that are causing

    the disease in question. Example: Cystic fibrosis (CF) is an inherited disease resulting from a

    single defective gene. One feature of the disease is the presence of excessive mucus in the

    respiratory tract that makes breathing difficult. If the normal CF gene is isolated from human

    DNA and then inserted into an attenuated virus such as the cold virus it can be applied to the

    lungs of a sufferer where in theory it should enter the epithelial cells of the patient. Having

    entered the human epithelial cells the inserted gene would function normally, the volume of

    mucus in the respiratory passages would be reduced and the patient would breathe more easily.


    Bk Ch7 S7.6 FQ3 7.6 Epidemiological studies FQA page 1 of 4

Copyright ? Pearson Australia (a division of Pearson Australia Group Pty Ltd)

Do some library or Internet research to find out about one of the following diseases.

    asbestosis mesothelioma asthma lung cancer emphysema coronary heart disease diabetes

In each case:

    ? describe the symptoms of the disease

    ? outline any long-term effects

    ? describe current treatments and prognoses

    ? summarise any apparent relationships between the disease and a causal factor indicated by

    statistics (include relevant statistics).


    Bk Ch7 S7.6 FA3 Example (mesothelioma):

    Mesothelioma is caused by exposure to asbestos. It is characterised by the appearance of a malignant

    tumour on the pleura, which is the lining of the lungs and chest cavity. Mesothelioma develops slowly

    and is usually diagnosed between 20 and 40 years after exposure, at which time the disease has already

    progressed so far as to signal imminent death. The symptoms include shortness of breath, coughing,

    chest pain, excessive sweating and weight loss. When diagnosed the mesothelioma tumour can be

    treated with radiation therapy or chemotherapy but this is usually unsuccessful. About 75% of patients

    die within 12 months of diagnosis. Statistics indicate a clear relationship between exposure to asbestos

    and the development of mesothelioma. There is no other known cause.


    Bk Ch7 S7.6 FQ4 Nuclear power stations are becoming increasingly common for generating electricity for domestic and

    industrial use around the world. But nuclear accidents involving dangerous releases of radiation, such

    as the accident in Japan in September 1999, are all too common.

    a What is radiation sickness? Describe its symptoms, treatment and prognosis.

    b What do epidemiological studies suggest about the long-term effects of exposure to high levels of

    radiation? Information related to the Three Mile Island incident and the Chernobyl disaster of

    1986 may be useful.


    Bk Ch7 S7.6 FA4 a Radiation sickness is the name given to a set of injuries or symptoms suffered by people who

    have had excessive exposure to radiation. Immediate symptoms include skin burns with blistering,

    nausea, vomiting, diarrhoea and fatigue; delayed symptoms include hair loss and inflammation of

    the mouth and throat. First aid measures involve removing the patient from the source of the

    radiation and washing the skin thoroughly with soap and water. Some of the symptoms of

    radiation sickness can be treated, but there is no treatment for the radiation itself. Depending on

    the dose received patients may die within two to four weeks of exposure. If patients survive this

    critical period they may eventually recover.

    b Long-term effects of excessive exposure to radiation such as that encountered at Chernobyl in

    1986 include the unusually high rate of cancer development. Cancers typical of high radiation

    exposure include leukaemia and thyroid cancer (associated with the release of radioactive iodine).


    Bk Ch7 S7.6 FQ5 Use reference books to help you complete the following table, summarising aspects of deficiency

    disease in humans.

Disease Cause Symptoms Treatment


    Anaemia Scurvy Beri-beri 7.6 Epidemiological studies FQA page 2 of 4

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    Pellagra Cretinism Marasmus Rickets Obesity Anorexia nervosa Bulimia Starvation


    Bk Ch7 S7.6 FA5

    Disease Cause Symptoms Treatment Kwashiorkor Protein deficiency in Lethargy, weight loss, Inclusion of protein in diet

    diarrhoea, dry skin, brittle infants after weaning

    hair, oedema

    Anaemia Iron deficiency Lack of energy, lethargy, Increase iron intakered

    meats, eggs, liver, lentils, pallor

    wholemeal cereals Scurvy Vitamin C (ascorbic acid) Swollen, tender gums; Increase vitamin C

    intakefresh fruits and deficiency susceptibility to bruising

    vegetables, especially

    citrus fruits Beri-beri Vitamin B (thiamin) Numbness in hands and Increased vitamin B 11feet, damage to nerves, intakewholegrain deficiency

    cereals, lean pork, liver, impaired heart function

    beans, peas, peanuts Pellagra Niacin (B group vitamin) Fatigue, headache, Increased niacin intake

    weight loss, loss of meat, poultry, fish, deficiency

    appetite, poor general peanuts

    health, tender tongue,

    sore mouth and throat,

    redness of tongue and

    lips, dermatitis, nausea

    and vomiting, confusion,

    dizziness, impaired

    memory, general


    Cretinism Iodine deficiency during Mental retardation, Treatment with thyroid

    impaired growth and poor hormone can improve foetal development

    development but damage development

    already sustained is

    irreversible Marasmus Deficiency of both protein Lethargy, severe weight Increased protein and

    and kilojoules in very loss, failure to grow, kilojoule intake

    impaired mental young infants


    Rickets Vitamin D (calciferol) Poor bone growth, Increased vitamin D

    curvature of the long intakemilk, egg yolk, deficiency

    fish and liver oils; the bones in the legs

    body also manufactures

    vitamin D when exposed 7.6 Epidemiological studies FQA page 3 of 4

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    to sunlight Obesity Excessive kilojoule intake Overweight; associated Balanced diet with

    disorders of the heart, adequate kilojoule intake

    weight-bearing joints and regular exercise Anorexia Psychological basis Weight loss, absence of Increased kilojoule intake

    manifested by extreme menstruation in females, associated with nervosa

    fear of eating, skewed counselling to remedy weight loss

    perception of own body underlying psychological

    shape problems Bulimia Psychological basis Episodes of binge-eating Counselling and

    followed by induced reassurance; may require

    vomiting; fatigue, hospitalisation

    depression, abnormal

    eating patterns,

    indigestion, urinary tract

    infections, constipation,

    irregular menstruation,

    heart irregularities

    Starvation Diet inadequate in the Weight loss, emaciation, Slowly increase food and

    extreme with severely lethargy, nausea, kilojoule intake,

    reduced food and maintaining balance of headache, diarrhoea

    kilojoule intake food groups

7.6 Epidemiological studies FQA page 4 of 4

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