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Human Biology (Year 12)

Gene Mutation Conditions

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Ben Whitten

What conditions do I need to know?

The two gene mutation conditions that you need to have an understanding of are:

  • Duchenne muscular dystrophy

  • Cystic fibrosis (CF)

What is Duchenne muscular dystrophy?

Duchenne muscular dystrophy is caused by a gene mutation and results in a wasting of the leg muscles, following by the arms, shoulders and chest.

The disease may occur through gene mutation, which may arise through a mutation in the mother which may then be inherited by her sons (as the gene affects the X chromosome). The mutation may also occur in a male zygote so that the child develops the disease.

DND usually becomes noticeable around 3-5 years of age, as muscle weakness becomes evident. Eventual death will result due to failure of the respiratory muscles, and boys are unlikely to live for more than 20-25 years with the condition.

What is Cystic fibrosis?

Cystic fibrosis is a genetic disorder that affects mostly the lungs, but also the pancreas, liver, kidneys, and intestine. Long-term issues include difficulty breathing and coughing up mucus as a result of frequent lung infections.

It is caused by a mutation which occurs in a huge gene on chromosome 7; the gene has the code for 1480 amino acids which makes up a protein that regulates the passage of chloride ions across the cell membrane.

Symptoms include:

  • Salty-tasting skin

  • Persistent coughing

  • Wheezing or pneumonia

  • Digestive/other problems

The allele is recessive, and so must be inherited from both parents.


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