Question

Which of the following diseases has autosomal recessive inheritance?

• A. Osteogenesis imperfecta
• B. Treacher Collins syndrome
• C. Achondroplasia
• D. Cystic fibrosis

Hint:

Autosomal recessive diseases require both parents to be carriers for the child to inherit the condition.

Answer 1

The Correct Option is D

To determine which of the given diseases has autosomal recessive inheritance, we need to understand the basic principles of genetic inheritance, particularly focusing on autosomal recessive inheritance.

1. Autosomal Recessive Inheritance: This type of inheritance means that two copies of the abnormal gene must be present for the disease or trait to develop. Usually, both parents of an affected individual are carriers, meaning they each possess one copy of the mutated gene but do not show symptoms themselves. Common features include the fact that the trait is not sex-linked (it appears equally in males and females) and a 25% chance of being affected if both parents are carriers.
2. Cystic Fibrosis: Cystic fibrosis (CF) is a well-known example of an autosomal recessive disorder. The disease is caused by mutations in the CFTR gene on chromosome 7. Since it follows an autosomal recessive pattern, individuals must inherit two defective CFTR genes, one from each parent, to exhibit symptoms of CF. This confirms that Cystic fibrosis is the correct answer.
3. Other Options:
   • Osteogenesis Imperfecta: This disease primarily follows an autosomal dominant pattern, although there are some rare recessive forms.
   • Treacher Collins Syndrome: This is primarily autosomal dominant, although rare autosomal recessive cases exist.
   • Achondroplasia: It is most commonly inherited in an autosomal dominant fashion.
   None of these are typically categorized as autosomal recessive except for rare exceptions, unlike cystic fibrosis.

In conclusion, Cystic fibrosis is the disease among the options provided that exhibits autosomal recessive inheritance. Understanding the pattern of genetic transmission and the specific gene mutations involved helps in accurately identifying the type of inheritance pattern for these diseases.