Characteristic of X-linked inheritance:

UP NHM CHO 7 Sept 2022 (Shift-2)

Pathology & Genetics

Easy

Appeared in: UP NHM CHO 7 Sept 2022 (Shift-2)

Explanation

In X-linked inheritance, the gene for the trait is located on the X chromosome.
Males have an XY chromosome pair, while females have an XX pair.
A father passes his Y chromosome to his sons and his X chromosome to his daughters.
Because sons inherit the Y chromosome from their father, it is impossible for a father to pass an X-linked trait to his son.
This absence of male-to-male transmission is a cardinal rule and a hallmark characteristic of X-linked inheritance.

Option B: This statement is biologically incorrect. A father has only one X chromosome, which he invariably passes on to all of his daughters.
Option C: While it is true that a father passes his X chromosome to his daughters, this is not the most defining or unique characteristic. The impossibility of father-to-son transmission is a more powerful rule for distinguishing X-linked from autosomal inheritance in pedigree analysis.
Option D: This statement is biologically incorrect for X-linked traits. Fathers determine the male sex of their offspring by passing on the Y chromosome, not the X chromosome.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Characteristics of X-linked genetic inheritance as background academic context rather than a clinical decision trigger.
Understanding inheritance patterns is crucial for genetic counseling. Nurses can help families understand their risk for genetic disorders like Hemophilia, Duchenne muscular dystrophy, and Fragile X syndrome, which are all X-linked.
When taking a family history, a nurse's recognition of patterns like the absence of male-to-male transmission can be a key first step in identifying a potential X-linked condition, prompting a referral for genetic testing and counseling.
Patient education is a key nursing role. Explaining to a father with an X-linked condition that he cannot pass it to his sons but that all his daughters will be carriers can alleviate guilt and provide clarity for family planning.

How to Approach the Question

First, recall the basic principles of sex determination: males are XY, and females are XX.
Next, remember how these chromosomes are passed on: fathers give their Y to sons and their X to daughters; mothers give an X to all children.
The term 'X-linked' means the gene is on the X chromosome.
Apply this logic to the father-son relationship: The son gets a Y from the father. Therefore, the father cannot pass his X chromosome to his son.
Evaluate each option based on this logic. Option A ('Father cannot pass to sons') directly matches this conclusion.
Eliminate the other options. A father must pass his X to his daughters, making options B and C either incorrect or less precise than A. Option D is incorrect because fathers pass the Y chromosome to sons.

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