In the below depicted pedigree of genetic disorders, Identify the disorder?

NORCET -4 , 2023

Pathology & Genetics

Hard

Appeared in: NORCET -4 , 2023

Explanation

The pedigree demonstrates vertical transmission, meaning the trait appears in every generation (I, II, and III), which is a hallmark of dominant inheritance.
There is clear evidence of male-to-male transmission, where an affected father in generation I passes the trait to his son in generation II.
This observation definitively rules out any form of X-linked inheritance, as a father contributes his Y chromosome, not his X chromosome, to his sons.
Affected individuals have at least one affected parent, and unaffected individuals do not pass the trait to their offspring, further supporting a dominant inheritance pattern.

Option A: Autosomal recessive disorders often skip generations, as unaffected carrier parents can have affected offspring. This pedigree shows the trait in every generation.
Option B: The term 'X-Linked disorder' usually implies X-linked recessive. This is incorrect because the pedigree shows male-to-male transmission, which is impossible for X-linked traits.
Option D: In X-linked dominant inheritance, an affected father passes the trait to all of his daughters and none of his sons. This pedigree shows an affected father with an affected son, which contradicts this rule.

Visual 1: Diagram - A simplified flowchart showing the steps to analyze a pedigree: 1. Check for vertical transmission (dominant) vs. skipping generations (recessive). 2. Check for male-to-male transmission (rules out X-linked). 3. Check ratios of affected males/females.

Clinical Relevance

Nursing practice connection: Knowing Pedigree analysis and modes of genetic inheritance helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Pedigree analysis is a fundamental tool in genetic counseling. It helps nurses and genetic counselors assess a family's risk for genetic conditions, provide accurate health information, and guide decisions about genetic testing.
Understanding inheritance patterns allows healthcare providers to predict the probability of a condition recurring in a family, which is crucial for family planning.
Examples of autosomal dominant disorders include Huntington's disease, Marfan syndrome, and neurofibromatosis type 1.

How to Approach the Question

First, analyze the overall pattern across generations. Does the trait appear in every generation? If yes, it's likely dominant. If it skips generations, it's likely recessive. In this case, it's in all three generations, suggesting a dominant pattern.
Next, look for clues to determine if it's autosomal or X-linked. The most definitive clue is male-to-male transmission (affected father to affected son).
Observe the relationship between the affected male in Generation I and his children in Generation II. You will see he has an affected son.
The presence of male-to-male transmission immediately rules out both X-linked dominant and X-linked recessive inheritance.
Combine the findings: The pattern is dominant and not X-linked. Therefore, it must be autosomal dominant.
Select the option that matches your conclusion.

Concept Tested & Keywords

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