Which causes Klinefelter syndrome?

Appeared in: RRB Nsg. Superintendent 21 July 2019 (shift 1st)

Explanation

Klinefelter syndrome is a genetic condition that occurs in males.
It is caused by the presence of one extra copy of the X chromosome, leading to a karyotype of 47,XXY.
This chromosomal error, known as aneuploidy, typically results from nondisjunction during parental meiosis (the formation of sperm or egg cells).
The presence of the Y chromosome determines the male phenotype, but the extra X chromosome leads to testicular dysfunction (hypogonadism) and other characteristic physical and developmental features.

Option A: The XO karyotype (also written as 45,X) results in Turner syndrome, not Klinefelter syndrome.
Option B: The XYY karyotype (47,XYY) causes Jacobs syndrome.
Option C: The XX karyotype (46,XX) is the typical chromosome constitution for a female.

Visual 1: Karyotype Diagram - An image showing a human karyotype for 47,XXY, highlighting the extra X chromosome in the sex chromosome pair, to help visualize the genetic abnormality.
Visual 2: Comparison Chart - A chart illustrating the key physical characteristics of individuals with Klinefelter syndrome, Turner syndrome, and Jacobs syndrome side-by-side.

Clinical Relevance

Nursing practice connection: Knowing Genetic basis of sex chromosome aneuploidies, specifically Klinefelter syndrome helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Nurses play a crucial role in identifying potential signs of Klinefelter syndrome during developmental assessments, such as delayed puberty, learning difficulties, or disproportionately long limbs.
Management involves a multidisciplinary team. Nursing care includes administering testosterone replacement therapy, providing psychological support for body image issues (e.g., gynecomastia) and learning disabilities, and offering fertility counseling.
What if? If a patient presented with short stature, a webbed neck, and had not started menstruating by age 15 (primary amenorrhea), the suspected diagnosis would shift from Klinefelter syndrome to Turner syndrome (45,XO).

How to Approach the Question

This is a factual recall question testing knowledge of medical genetics.
First, identify the core concept in the question stem, which is 'Klinefelter syndrome'.
Recall the specific chromosomal abnormality associated with this syndrome from your studies.
Systematically evaluate each option: 'XO' is linked to Turner syndrome, 'XYY' to Jacobs syndrome, 'XX' is the normal female karyotype, and 'XXY' is the classic karyotype for Klinefelter syndrome.
Select the option that correctly matches the genetic cause with the named syndrome.

Concept Tested & Keywords

Concept Tested: Genetic basis of sex chromosome aneuploidies, specifically Klinefelter syndrome.
Stem keywords: Klinefelter syndrome, causes
Lead-in keywords: Which

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Practise the full RRB Nsg. Superintendent 21 July 2019 (shift 1st)

Attempt every question from this paper in a timed mock, then review the full solution for each one.