When we look into genetics in Year 10 Biology, it’s really interesting to learn about two types of genetic disorders: autosomal dominant and autosomal recessive. Let’s break down how they are different.

1. How They Are Passed Down

• Autosomal Dominant Disorders:

  • You only need one copy of the altered gene from either parent to be affected by these disorders.
  • If one parent has the disorder, there is a 50% chance they might pass it on to their child.
  • For example, if we use “A” for the affected gene and “a” for the normal gene, a parent with “Aa” could pass either “A” or “a” to their child.

• Autosomal Recessive Disorders:

  • These disorders need both parents to pass on a copy of the altered gene for their child to be affected.
  • If both parents are carriers (meaning each has one normal gene and one altered gene, “Aa”), there is a:
    • 25% chance their child will be affected (“aa”).
    • 50% chance the child will be a carrier like the parents (“Aa”).
    • 25% chance the child will be normal and not a carrier (“AA”).

2. Examples of Disorders

• Common Autosomal Dominant Disorders:

  • Examples include Huntington’s disease and Marfan syndrome. If one parent has one of these disorders, their children have a 50/50 chance of inheriting it.

• Common Autosomal Recessive Disorders:

  • Conditions like cystic fibrosis and sickle cell anemia are part of this group. For a child to be affected, both parents must be carriers.

3. Symptoms of the Disorders

• Symptoms in Dominant Disorders:

  • Symptoms usually show up in adults because these diseases often don’t appear until later in life.

• Symptoms in Recessive Disorders:

  • Symptoms can show up in childhood since both altered genes need to be there from the beginning.

Learning about these differences helps us understand how traits and disorders can be passed down through families. Genetics can be really complex, but it’s also really exciting!