Which is a genetic disorder found in females due to absence of a normal second sex chromosome?

ESIC Nursing Officer 2016 (shift-1)

Pathology & Genetics

Easy

Appeared in: ESIC Nursing Officer 2016 (shift-1)

Explanation

Turner syndrome is a chromosomal disorder affecting females where one of the X chromosomes is partially or completely missing.
The most common karyotype is 45,X, which is a form of monosomy (the loss of a chromosome).
This absence of a second sex chromosome leads to a distinct set of clinical features, including short stature, gonadal dysgenesis (streak ovaries), and a webbed neck.
The condition occurs in about 1 in 2,500 female live births and is a common cause of primary amenorrhea.

Option B: Rett's disorder is a neurodevelopmental disorder caused by a mutation in the MECP2 gene on the X chromosome, not by the absence of an entire chromosome.
Option C: Asperger's disorder, now part of Autism Spectrum Disorder (ASD), is a neurodevelopmental condition with a complex genetic and environmental basis. It is not a chromosomal aneuploidy (abnormal number of chromosomes).
Option D: Down syndrome is caused by the presence of an extra chromosome 21 (Trisomy 21). It involves an additional chromosome, not a missing one, and it is an autosomal (non-sex chromosome) disorder.

Visual 1: Karyotype Diagram - A comparison of a normal female karyotype (46,XX) and a Turner syndrome karyotype (45,X) to visually demonstrate the missing chromosome.
Visual 2: Infographic - An infographic detailing the common clinical features of Turner Syndrome, such as short stature, webbed neck, shield chest, and associated cardiac/renal anomalies.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Chromosomal abnormalities and associated genetic disorders as background academic context rather than a clinical decision trigger.
Early diagnosis of Turner syndrome is crucial for timely management, including growth hormone therapy to address short stature and estrogen replacement therapy to induce puberty and maintain secondary sexual characteristics.
Nurses play a key role in identifying potential signs at birth (e.g., lymphedema), providing patient and family education, offering emotional support, and coordinating care with endocrinologists and cardiologists.
What if? If a patient were male and had an extra X chromosome (47,XXY), the condition would be Klinefelter syndrome, which is characterized by hypogonadism, tall stature, and gynecomastia.

How to Approach the Question

First, break down the question to identify the core requirements: 1) a genetic disorder, 2) found in females, and 3) caused by the absence of a second sex chromosome.
Review the options one by one and evaluate them against these criteria.
Recall or deduce the genetic basis of each disorder. Turner syndrome is defined by monosomy X (XO).
Eliminate options that do not fit. Down syndrome is a trisomy (extra chromosome). Rett's is a gene mutation. Asperger's is a neurodevelopmental disorder without a simple chromosomal number change.
Confirm that Turner syndrome matches all parts of the question's definition. The provided image also directly illustrates the features of Turner syndrome, reinforcing the correct choice.

Concept Tested & Keywords

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