Question
What is the inheritance pattern shown in the given pedigree?
| A. |
Autosomal Dominant
|
| B. |
Autosomal Recessive
|
| C. |
X-linked Recessive
|
| D. |
X-linked Dominant
|
Show Answer
|
Correct Answer » A
Explanation
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|
Features Seen in the Pedigree
- Affected individuals are present in successive generations (vertical transmission).
- Both males and females are affected.
- Male-to-male transmission is present:
- Individual 4 → Individual 9
- An affected parent transmits the disorder to approximately half of the offspring.
- Unaffected individuals do not transmit the disease.
These features are characteristic of Autosomal Dominant inheritance.
Reasons to Rule Out Other Options
B. Autosomal Recessive
- Usually skips generations.
- Often appears among siblings rather than every generation.
- Affected children commonly born to unaffected carrier parents.
- Not consistent with this pedigree.
C. X-linked Recessive
- Typically affects males predominantly.
- No male-to-male transmission occurs.
- Presence of father-to-son transmission rules it out.
D. X-linked Dominant
- Affected fathers transmit disease to all daughters and no sons.
- Here, affected father (4) has an affected son (9), which excludes X-linked dominant inheritance.
