Lesson 7 Single Gene Disorders (H)


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Lesson 7 Single Gene Disorders (H)

  1. 1. Single gene disorders <ul><li>Aims: </li></ul><ul><li>Recall a small number of disorders are caused by alleles of a single gene </li></ul><ul><li>Recall the symptoms of Huntington’s disorder and cystic fibrosis </li></ul><ul><li>Understand why a person with one recessive allele will not show the associate characteristics but may pass these on to their children. </li></ul>
  2. 2. True or false? <ul><li>Most features are controlled by a single allele </li></ul><ul><li>False </li></ul><ul><li>A disorder caused by many genes is easy to understand </li></ul><ul><li>False </li></ul><ul><li>Genes come in pairs </li></ul><ul><li>True </li></ul><ul><li>An inherited disease cannot be caught from somebody else </li></ul><ul><li>True </li></ul><ul><li>A healthy diet during pregnancy can prevent cystic fibrosis </li></ul><ul><li>False </li></ul>
  3. 3. Symptoms of Huntington's disease <ul><li>Read the stories below and list the symptoms of Huntington's disease </li></ul><ul><li>Craig's story </li></ul><ul><li>My grandfathers only 56. he’s always been well but now he’s a bit off colour. </li></ul><ul><li>He’s been forgetting things – driving my Nan mad. No one’s said anything to me, but they’re worried about him. </li></ul><ul><li>Craig’s grandfather, Robert </li></ul><ul><li>I'm so frustrated with myself. I cant sit still in a chair. </li></ul><ul><li>I'm getting more and more forgetful. Now I’ve started falling over for no reason at all. The doctor said it might be Huntington's disorder, its an inherited condition. She said I can have a blood test to find out, but I’m very worried. </li></ul>
  4. 4. Symptoms of Huntington's <ul><li>The symptoms first appear in middle age </li></ul><ul><li>At first people have problems with muscle control (twitching). </li></ul><ul><li>People become forgetful. </li></ul><ul><li>They become confused and find it hard to understand things. </li></ul><ul><li>After a few years they cannot control their movements. </li></ul><ul><li>Sadly, the condition is fatal. </li></ul>
  5. 5. Cystic fibrosis <ul><li>Watch video here or read story before listing the symptoms of cystic fibrosis. </li></ul>
  6. 6. What is Cystic fibrosis? <ul><li>Most people with cystic fibrosis cannot have children. The thick mucus affects their reproductive systems. So babies with CF are usually born to healthy parents. At first- this seems strange. </li></ul><ul><li>How can a parent pass on a disease to their children when they don’t have it themselves? </li></ul><ul><li>You cant catch cystic fibrosis, it is a genetic disorder. The disease causes big problems for breathing and digestion. Cells that make mucus in the body don’t work properly. The mucus is much thicker than it should be so it blocks up the lungs. It also blocks tubes that take enzymes from the pancreas to the gut. People with cystic fibrosis get breathless. </li></ul><ul><li>They also get many chest infections. </li></ul><ul><li>The shortage of enzymes in their gut means their food is not digested properly, so they can be short of nutrients. </li></ul>
  7. 7. Symptoms of Cystic fibrosis <ul><li>You should have - </li></ul><ul><li>Problems with breathing and digestion. </li></ul><ul><li>Cells making mucus in the body are not working properly. </li></ul><ul><li>Mucus is much thicker than it should be- (lung blockage) </li></ul><ul><li>Mucus blocks tubes taking enzymes from the pancreas to the gut. </li></ul><ul><li>They get many chest infections. </li></ul><ul><li>1 in 25 people in the UK carrier the allele for cystic fibrosis </li></ul>
  8. 9. Family tree- Huntington's Woman with Huntington’s Man with Huntington’s Woman without Huntington’s Man without Huntington’s Liam Kate Lisa Susan Sarah Karl Paul Emma Sean Alex Jo John
  9. 10. Family tree – Cystic fibrosis Rob David Shane Paula Jane Laura Keith Leon Owen Claire Sian Man with out cystic fibrosis Man with cystic fibrosis Woman without cystic fibrosis Woman with cystic fibrosis
  10. 11. Questions linked to the family trees <ul><li>Huntington's disease </li></ul><ul><li>How many people have Huntington's disease? </li></ul><ul><li>What is Sarah’s genotype? </li></ul><ul><li>What is Karl's genotype? </li></ul><ul><li>What are the chances of Jo and Paul having children with Huntington's disease? </li></ul><ul><li>Cystic Fibrosis </li></ul><ul><li>How many people have cystic fibrosis? </li></ul><ul><li>Explain why Shane has cystic fibrosis even though his parents don’t. </li></ul><ul><li>Explain why Laura has cystic fibrosis even though her parents don’t. </li></ul><ul><li>How could you change the family tree so that it shows carriers how cystic fibrosis? </li></ul><ul><li>Who do you think are carriers in this family tree? </li></ul>
  11. 12. Comparing patterns of inheritance What are the possible allele pairs of people without the disorder? What are the possible allele pairs of people with the disorder? Do the parents of the affected people also have the disease? Cystic fibrosis Huntington’s Name of disorder Key: H = Huntington's allele C = normal allele h = normal allele c = cystic fibrosis allele
  12. 13. Summary of cystic fibrosis and Huntington's Disease <ul><li>What do people mean when they say ‘cystic fibrosis can be completely unexpected’? </li></ul><ul><li>What does it mean to be a ‘carrier’? </li></ul><ul><li>Who are carriers in the two family trees? (think about it) </li></ul><ul><li>Describe the difference between the inheritance of cystic fibrosis and Huntington’s disease using the word ‘alleles’. </li></ul><ul><li>Use a fully labelled genetic cross to determine the probability of </li></ul><ul><li>a female carrier and a normal male having a child with cystic fibrosis </li></ul><ul><li>a female carrier and a male carrier having a child with cystic fibrosis. </li></ul><ul><li>c) a heterozygous man with Huntington's and a normal female having a child with Huntington's. </li></ul>
  13. 14. Inheriting Cystic fibrosis - summary <ul><li>Cystic fibrosis is caused by one of the thousands of genes responsible for producing a human being. There are two versions (alleles) of this gene. The first is dominant and instructs cells to make normal mucus, the second is recessive and which leads to the symptoms of cystic fibrosis. </li></ul>