Explanation:
Let’s go step by step using the pedigree rules given:
1.
Males = squares,
Females = circles
- Darkened (filled) = has hemophilia
- Clear (open) = normal blood clotting
We’ll count individuals by generation (I to IV), left to right.
Generation I:
- 1: square (male), open → normal male
- 2: circle, filled → female with hemophilia
→ Males: 1
→ Females: 1
Generation II:
- 3: circle, open → normal female
- Next: circle, open → normal female
- Next: square, open → normal male
→ Males: 1
→ Females: 2
Generation III:
- First: square, open → normal male
- Second: circle, open → normal female
- Third: square, filled → male with hemophilia
- Fourth: circle, open → normal female
→ Males: 2 (one filled)
→ Females: 2
Generation IV:
From left to right:
1. square, filled → male with hemophilia
2. circle, open → normal female
3. square, filled → male with hemophilia
4. circle, filled → female with hemophilia
5. square, open → normal male
6. square, open → normal male
7. circle, open → normal female
→ Males: 4 (positions 1, 3, 5, 6)
→ Females: 3 (positions 2, 4, 7)
Now total up:
Total males = Gen I (1) + Gen II (1) + Gen III (2) + Gen IV (4) =
8 ✔
Males with hemophilia = Gen I (0) + Gen II (0) + Gen III (1) + Gen IV (2) =
3 ✔
(III-3 and IV-1 and IV-3 — all darkened squares)
Total females = Gen I (1) + Gen II (2) + Gen III (2) + Gen IV (3) =
8 ✔
Females with hemophilia = Gen I (1: II-2) + Gen II (0) + Gen III (0) + Gen IV (1: IV-4) =
2 ✔
Marriages = horizontal lines connecting a circle and a square:
- I-1 (♂) ↔ I-2 (♀) → 1
- II-3 (♀) ↔ II-4 (♀)? No — wait, marriage is only between circle and square. Let's check carefully:
Look at connections:
- I-1 (square) — horizontal line to I-2 (circle) → marriage #1
- II-3 (circle) — horizontal line to II-4 (circle)? No, that’s not a marriage. Actually, in standard pedigrees, siblings are connected *under* parents, not horizontally to each other.
Correct way: Marriage lines are horizontal lines *between* a male and female who produce offspring.
From the diagram:
1. I-1 (♂) and I-2 (♀) → have children II-3 and II-4 → marriage #1
2. II-4 (♀) and II-5 (♂) → they’re connected by horizontal line, and have children III-1, III-2, III-3, III-4? Wait — let’s trace:
Actually, looking at structure:
- II-3 (♀) and II-4 (♀) are sisters (both children of I-1 & I-2).
- Then II-4 (♀) marries II-5 (♂) — yes, horizontal line between them → marriage #2
- III-3 (♂, hemophiliac) marries III-4 (♀) — horizontal line → marriage #3
So total marriages =
3 ✔ (as answer key shows).
All answers match the provided answer key.
Final Answer:
1a. 8
1b. 3
2a. 8
2b. 2
3a. 3
Parent Tip: Review the logic above to help your child master the concept of pedigree practice worksheet.
