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					          KS4 Biology




                        Inherited Diseases

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          Contents

                     Inherited Diseases


               Cystic fibrosis
               Sickle cell anaemia
               Huntington’s disease




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          What is cystic fibrosis?
          Cystic fibrosis is an inherited
          disease that affects many
          body organs, particularly the
          lungs and digestive system.
          The air passages in healthy
          lungs are coated with a
          constant flow of mucus, which
          traps and removes bacteria.
          In a person with cystic fibrosis,
          mucus is thicker than normal.
          This thick, sticky mucus can block
          the lungs and airways. How will this
          affect a person with cystic fibrosis?

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          What is cystic fibrosis?
          A person with cystic fibrosis
          has breathing difficulties.
          They are at risk of repeated
          chest infections which can
          lead to lung damage.

          People with cystic fibrosis
          need daily physiotherapy,
          which involves massage to
          help loosen the sticky mucus.
          Antibiotics help to treat and
          control lung infections and
          prevent lung damage.

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          What is cystic fibrosis?
          Treatment for the cystic fibrosis
          also includes special inhalants.
          In severe cases, a lung transplant
          operation is required.




          People with cystic fibrosis can
          have problems digesting food.
          Most take enzyme pills when
          they eat to supply missing
          enzymes and allow digestion.


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          Living with cystic fibrosis
          Over 7,500 people in the UK
          are affected by cystic fibrosis.




          Children born with cystic
          fibrosis do not have a normal
          life expectancy, although this
          is improving all the time.



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          How is cystic fibrosis inherited?
          Cystic fibrosis is caused by a recessive allele.
          What symbols could stand for the different forms of this gene?

                  c =          cystic fibrosis allele


                  C =           normal allele

          What alleles has a person with cystic fibrosis inherited?

                                   c c
          A person with cystic fibrosis has the genotype cc.
          They have inherited a cystic fibrosis gene from both parents.

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          How is cystic fibrosis inherited?
          How do you represent the genotype of a person
          who inherits one cystic fibrosis allele?

                                C c

    Does a person with this genotype have cystic fibrosis?
    A heterozygous person (Cc) is called a carrier.
    They do not have the disease but they do carry the cystic
    fibrosis allele which they might pass on to their children.

    In the UK, 2.3 million people carry the cystic fibrosis gene.



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          Cystic fibrosis inheritance activity 1




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           Cystic fibrosis inheritance activity 2




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           Contents

                      Inherited Diseases


                Cystic fibrosis
                Sickle cell anaemia
                Huntington’s disease




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           What is sickle cell anaemia?
           Sickle cell anaemia is an
           inherited disease that
           affects red blood cells.
           Normal red blood cells
           contain haemoglobin,
           a protein that carries
           oxygen around the body.
           In sickle cell anaemia,
           red blood cells have
           abnormal haemoglobin.
           This distorts red blood
           cells to form curved,
           sickle shapes.


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           What is sickle cell anaemia?
           Normal red blood cells are
           shaped so that they move
           easily through blood vessels.
           This ensures that oxygen is
                                           normal cells
           delivered to the body.
                                           move freely
           Sickle-shaped red blood cells
           can get stuck in narrow blood
           vessels and cause blockages.
           Oxygen is prevented from
           getting to the body’s tissues
           and organs. This leads to       sickle cells
           severe pain and can cause        get stuck
           permanent organ damage.
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           What is sickle cell anaemia?
           Red blood cells normally have
           a lifetime of about 4 months.
           Sickle cells are fragile and
           only last for 10–20 days.




           The shorter lifetime of sickle cells reduces the number of
           red blood cells leading to anaemia.
           People with anaemia feel weak and tired.
           Children with sickle cell anaemia are able to lead normal
           lives but need regular medical attention. Treatment
           sometimes includes blood transfusions.
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           Who is affected by sickle cell anaemia?
           It is estimated that there
           are around 6,000 people
           affected by sickle cell
           disorders in Britain.



           Sickle cell anaemia mostly
           affects people of African
           descent, but people from
           India, the Mediterranean
           and Middle East are also
           affected.



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           What causes sickle cell anaemia?
           Sickle cell anaemia is caused by a recessive allele.
           What symbols could stand for the different forms of this gene?

                           s =          sickle cell allele


                           S =          normal allele

           What alleles has a person with sickle cell anaemia inherited?


                                    s s
           A person with sickle cell anaemia has inherited two sickle
           cell alleles, one from each parent.
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           What causes sickle cell trait?
           What is the genotype of a person who has inherited
           one sickle cell allele?

                                     S s
           Does a person with this genotype have sickle cell anaemia?
           The sickle cell allele is recessive so this person does not
           have the disease. They are a carrier of the sickle cell allele.




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           Sickle cell anaemia inheritance activity




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           Contents

                      Inherited Diseases


                Cystic fibrosis
                Sickle cell anaemia
                Huntington’s disease




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           What is Huntington’s disease?
           Huntington’s disease is an inherited
           disease that affects the brain and
           central nervous system.

           The wide-ranging symptoms of this
           inherited condition usually develop
           in adults between the ages of 30 and 50 .

           Huntington’s disease causes damage
           to nerve cells in the areas of the brain
           involved in the control of movement,
           planning and motivation.

           How will this affect a person with
           Huntington’s disease?
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           What is Huntington’s disease?
           People with Huntington’s disease are
           affected by gradual physical, mental
           and emotional changes.
           The early symptoms of Huntington’s
           disease include:
            mild tremor
            clumsiness
            lack of concentration
            problems remembering things
            depression
            mood changes, sometimes including aggressive behaviour.
           People can have symptoms for several years before
           finding out they have Huntington’s disease.
           Why can it take so long for this disease to be diagnosed?
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           What is Huntington’s disease?
           The physical, mental and emotional
           symptoms of Huntington’s disease
           become progressively worse.
           As the disease continues, people may
           experience involuntary movements,
           weight loss, speech problems and
           extensive memory loss. Eventually
           a person with Huntington’s disease
           needs complete nursing care.
           Currently there is no cure for Huntington’s disease.
           Medication is available to help treat some symptoms such
           as involuntary movements, depression and mood swings.
           Around 4,800 people in the UK have Huntington’s disease.

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           How is Huntington’s disease inherited?
           Huntington’s disease is caused by a dominant allele.
           What symbols could stand for the different forms of this gene?

                        H =           Huntington’s allele

                        h =           normal allele

           If someone inherits one Huntington’s disease allele will they
           develop the disease?

                                    H h
           The Huntington’s disease allele is dominant, so inheriting
           one allele from either parent will lead to this condition.
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           How is Huntington’s disease inherited?
           Huntington’s disease is caused by a
           dominant allele and can be passed on
           by one parent who has the disease.

           Anyone who inherits the Huntington’s
           allele will develop the disease, usually
           between the ages of 30 and 50.

           People with the Huntington’s allele may have had a family
           before realizing that they have inherited the disease.

           If one parent has the Huntington’s allele and the other is a
           non-carrier, what is the chance that their children will have
           Huntington’s disease?


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           Huntington’s disease inheritance activity




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