Question

Consider the following diseases:
1. Huntington's disease
2. Cystic fibrosis
3. Sickle Cell anaemia
4. Haemophilia A
Which of the following disorders are transmitted as autosomal recessive genetic disorders?

• A. 1, 2 and 4
• B. 1 and 2
• C. 2 and 3
• D. 3 and 4

Hint:

Recall which of these four diseases need two faulty gene copies on an autosome.

Answer 1

The Correct Option is C

Step 1: Understanding the Question.
Four inherited diseases are listed: Huntington's disease, Cystic fibrosis, Sickle Cell anaemia, and Haemophilia A. We need to pick the two that follow an autosomal recessive pattern of inheritance.

Step 2: Key Concept.
In autosomal recessive disease, the faulty gene sits on a non sex chromosome (autosome) and a person needs two copies of the faulty gene, one from each parent, to show the disease. Autosomal dominant disease needs only one faulty copy, and X linked disease sits on the X chromosome and affects mainly males.

Step 3: Sort each disease by inheritance pattern.
Huntington's disease is autosomal dominant, one faulty copy of the HTT gene on chromosome 4 is enough to cause the disease, and it usually shows up in more than one generation of a family.
Cystic fibrosis is autosomal recessive, caused by mutations in the CFTR gene on chromosome 7, and needs two faulty copies.
Sickle Cell anaemia is autosomal recessive, caused by a mutant beta globin gene on chromosome 11, and again needs two faulty copies to cause full blown disease.
Haemophilia A is X linked recessive, the faulty factor VIII gene sits on the X chromosome, so it mainly affects males who inherit the single faulty X from their mother.

Step 4: Match with the options.
Only Cystic fibrosis (2) and Sickle Cell anaemia (3) are autosomal recessive. Huntington's disease is dominant, not recessive, and Haemophilia A is X linked, not autosomal. So the combination "2 and 3" is correct.

Step 5: Final Answer.
The disorders transmitted as autosomal recessive are
\[ \boxed{\text{Cystic fibrosis and Sickle Cell anaemia (2 and 3)}} \]