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Science

DNA

Alleles and genetic disorders

Alleles

Different forms of the same genegene: The basic unit of genetic material inherited from our parents. A gene is a section of DNA which controls part of a cell's chemistry - particularly protein production. are called alleles - pronounced 'al-eels'. You inherit one allele for each gene from your father and one allele for each gene from your mother. For example, the gene for eye colour has an alleles for blue eye colour and an alleles for brown eye colour. Your eye colour will depend on the combination of alleles you have inherited from your parents.

Genetic disorders

Diseases can be caused by a number of things, including:

  • infections eg influenza
  • poor diet eg scurvy
  • environmental factors eg asbestosis
  • spontaneous degeneration of tissues eg multiple sclerosis

Some diseases are inherited from our parents through our genes: they are called genetic disorders. They occur because of faulty alleles. Cystic fibrosis is an example of a genetic disorder.

Cystic fibrosis

People with cystic fibrosis have inherited two faulty alleles, one from their father and one from their mother. They produce unusually thick and sticky mucusmucus: Slimy white protein, which lines the respiratory tract and alimentary canal. in their lungs and airways. Their lungs become congested with mucus, and they are more likely to get respiratory infections. Daily physiotherapy helps to relieve congestion, while antibiotics [antibiotics: Substances that kill bacteria. ] are used to fight infection. The disorder also affects the gut and pancreas, so that food is not digested efficiently.

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