Have you read the post regarding genetic diagrams in I/GCSE Biology. In this post, we'll move on talking about how genetic diseases are caused!

Do you remember what alleles are in I/GCSE Biology?

• Different forms of the same gene are called ALLELES.
• 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 alleles for blue eye colour and alleles for brown eye colour.
• Your eye colour will depend on the combination of alleles you have inherited from your parents.
• Some diseases are inherited from our parents though our genes: they are called GENETIC DISORDERS.
• They occur because of faulty or defective alleles.

Then, let's look at some examples of genetic diseases in I/GCSE Biology!

• Cystic fibrosis is caused by a recessive allele. You need to inherit two copies of the faulty allele to be born with cystic fibrosis. If you have just one copy, you are a CARRIER

Cystic fibrosis affects the cell membranes causing a THICK MUCUS to be produced in the lungs, gut and pancreas.

SYMPTOMS

1. Thick and sticky mucus
2. Breathing problems
3. Chest infections
4. Difficulty digesting food

In I/GCSE Biology, it's important to know what huntington's disease too!

HUNTINGTON’S DISEASE is another genetic that affects the central nervous system. 

• However is caused by a dominant allele – the presence of just one dominant allele can cause the disease.
• You only need to inherit one copy of the faulty allele to have Huntington’s disorder, unlike cystic fibrosis, where you need to inherit both copies.
• You can inherit the disorder if one or both of your parents carry the faulty allele, because it is DOMINANT.

SYMPTOMS:

1. Uncontrollable shaking
2. Clumsiness
3. Memory Loss   
4. Inability to concentrate
5. Mood changes

And we're done with this topic! Well Done!

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 References:

1. "Genetic diseases", https://www.mayoclinic.org/-/media/kcms/gbs/patient-consumer/images/2013/11/19/10/05/ds00549-autosomal-dominant-inheritance-pattern.jpg
2. "Cystic fibrosis". Photo from the internet.
3. "Cystic fibrosis", https://upload.wikimedia.org/wikipedia/commons/9/9a/Cysticfibrosis01.jpg
4. "HUNTINGTON’S DISEASE". Photo from the internet.
5. "Huntington's Disease", https://i.ytimg.com/vi/M6Z9bkd7zF8/mqdefault.jpg