Sickle cell anemia is?

ISRO- 2016

Pathology & Genetics

Easy

Appeared in: ISRO- 2016

Explanation

Sickle cell anemia is an autosomal recessive disorder, meaning an individual must inherit two copies of the mutated HBB gene, one from each parent, to express the disease.
The HBB gene is located on chromosome 11, which is an autosome (non-sex chromosome), so the condition affects males and females equally.
If both parents are carriers (heterozygous, HbAS), there is a 25% chance with each pregnancy of having a child with sickle cell anemia (homozygous, HbSS).
Individuals who are heterozygous (carriers) have the sickle cell trait but are typically asymptomatic because the normal allele produces enough functional hemoglobin.

Option A: This pattern involves a dominant gene on the X chromosome. Sickle cell anemia is caused by a recessive gene on an autosome (chromosome 11), not a sex chromosome.
Option B: This pattern involves a recessive gene on the X chromosome and primarily affects males. Sickle cell anemia affects males and females with equal frequency.
Option C: This pattern requires only one copy of the mutated gene to cause the disease. Sickle cell anemia requires two copies of the mutated gene.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Genetic Inheritance of Diseases as background academic context rather than a clinical decision trigger.
Nurses play a crucial role in educating families about genetic counseling, particularly if there is a family history of sickle cell disease or if they belong to high-risk populations.
Understanding the carrier state (sickle cell trait) is vital. Carriers are usually asymptomatic but can pass the gene to their children, making family planning education essential.
Newborn screening for sickle cell disease is standard in many countries, allowing for early diagnosis and intervention to prevent complications.

How to Approach the Question

Identify the core concept: The question asks for the genetic inheritance pattern of a specific disease, sickle cell anemia.
Recall the definitions of the different inheritance patterns provided in the options: autosomal vs. X-linked, and dominant vs. recessive.
Differentiate 'autosomal' (gene on a non-sex chromosome, affects males and females equally) from 'X-linked' (gene on the X chromosome, often shows sex-differentiated patterns).
Differentiate 'recessive' (two copies of the gene needed for the disease to be expressed) from 'dominant' (only one copy is needed).
Apply this knowledge to sickle cell anemia, a classic example in genetics. Recall that it requires two copies of the sickle cell gene and is not linked to sex chromosomes.
Conclude that this matches the definition of an autosomal recessive disorder.

Concept Tested & Keywords

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E6 Textbook of Biochemistry for medical StudentsDM Vasudevan Part 2 — Subpart B (pp 240-463 of 478) p. 25-27

E6 Pathology- ROBBINS & COTRAN PATHOLOGIC BASIS OF DISEASE 10TH Ed pp. 153-155, 151-153