16.2.7

Specific Mutations

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Specific Mutations

There are some specific mutations you need to know for the exam:

Illustrative background for AlbinismIllustrative background for Albinism ?? "content

Albinism

  • Albinism is a recessive condition where individuals are unable to produce the pigment melanin.
  • This is due to mutations in the TYR gene. The TYR gene codes for a tyrosinase enzyme.
  • Tyrosinase is responsible for catalysing the production of melanin in pigment-producing cells called melanocytes.
    • Melanin is the pigment which gives skin, hair, and the iris of the eye colour.
  • Individuals with albinism have light-coloured skin & hair. They may also have vision problems due to melanin's role in the eye.
Illustrative background for Sickle cell anaemia Illustrative background for Sickle cell anaemia  ?? "content

Sickle cell anaemia

  • Sickle cell anaemia is a recessive condition where individuals have sickle-shaped red blood cells.
  • It is caused by a mutation in the gene which codes for the beta chain of haemoglobin. It is a missense mutation.
  • The change of shape to sickled means that red blood cells are able to carry less oxygen.
  • Individuals with sickle-celled anaemia can suffer from anaemia, pain, and increased risks of stroke.
Illustrative background for Haemophilia Illustrative background for Haemophilia  ?? "content

Haemophilia

  • Haemophilia is an X-linked recessive condition in which individuals blood does not colour correctly.
    • Individuals with haemophilia have difficulty clotting blood. This means they bleed for longer than they should. This can be a problem following trauma.
  • Blood clotting is controlled by multiple factors. Haemophilia results due to mutations in clotting factor VIII or IX.
  • The genes for these factors are located on the X-chromosome. So, we say this condition is "X-linked".
Illustrative background for Huntingdon's disease Illustrative background for Huntingdon's disease  ?? "content

Huntingdon's disease

  • Huntingdon's disease is a dominant condition due to a mutation in the HTT gene. The HTT codes dor the huntingtin protein.
  • Mutations in the huntingtin protein cause premature degeneration of brain nerve cells. This degeneration leads to a variety of symptoms:
    • In the early stages of the disease, individuals develop jerky, uncontrollable movements called chorea.
    • Neuropsychiatric symptoms such as anxiety, depression, and irritability.
    • Cognitive abilities such as planning are also impacted.

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1Cell Structure

2Biological Molecules

3Enzymes

4Cell Membranes & Transport

5The Mitotic Cell Cycle

6Nucleic Acids & Protein Synthesis

7Transport in Plants

8Transport in Mammals

9Gas Exchange

10Infectious Diseases

11Immunity

12Energy & Respiration (A2 Only)

13Photosynthesis (A2 Only)

14Homeostasis (A2 Only)

15Control & Coordination (A2 Only)

16Inherited Change (A2 Only)

17Selection & Evolution (A2 Only)

18Classification & Conservation (A2 Only)

19Genetic Technology (A2 Only)

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