Final Answer:
The pedigree shows an autosomal dominant inheritance pattern.
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Explanation:
Let’s walk through how we figure this out step by step.
1.
What do the symbols mean?
- Squares = males, circles = females
- Filled (black) = affected (has the trait), empty = unaffected
2.
Look at the top generation (parents):
- Both parents are affected (filled square and circle).
- They have 5 children: 3 affected (2 black, 1 black), 2 unaffected (empty circles).
→ So, affected parents can have unaffected children. That rules out *autosomal recessive* (because if both parents were homozygous recessive, all kids would be affected — but here they’re not). It also rules out *X-linked recessive* for similar reasons.
3.
Check if it could be X-linked dominant:
- In X-linked dominant, an affected father passes the trait to *all* his daughters (since he gives them his only X chromosome), but *none* of his sons.
- Look at the affected father in the top row: he has 2 daughters — one is affected (black circle), one is unaffected (empty circle).
→ Since one daughter is unaffected, it cannot be X-linked dominant.
4.
Now check autosomal dominant:
- Affected individuals have at least one affected parent (true here — all affected people trace back to affected ancestors).
- The trait appears in every generation (no skipping) — yes, it’s present in generation I, II, and III.
- Affected parents can have unaffected children (yes — e.g., top couple has 2 unaffected kids).
- Males and females are affected roughly equally (we see 4 affected males and 3 affected females — close enough for a small pedigree).
All these fit
autosomal dominant.
So the answer is: autosomal dominant inheritance.
Parent Tip: Review the logic above to help your child master the concept of pedigree practice problems worksheet.
