Pedigree Chart Introduction worksheet - Free Printable

Let’s go step by step to solve each question based on the pedigree chart.

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First, understand the symbols:

- Squares = males
- Circles = females
- Filled shapes = have blue eyes (recessive trait, so genotype must be bb)
- Empty shapes = do NOT have blue eyes (so they have at least one B — could be BB or Bb)
- Horizontal line between two shapes = marriage
- Vertical line down from a marriage = children

Also given:
> Blue eyes is recessive → only bb shows blue eyes
> Brown eyes = BB or Bb

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Question 1:

a) How many males are shown in this pedigree?

Look for all squares:

Generation I:
- Male 1 → 1 male

Generation II:
- Male 1, Male 3, Male 4 → 3 males

Generation III:
- Male 1, Male 3, Male 4, Male 5 → 4 males

Total males = 1 + 3 + 4 = 8

✔ Answer: 8

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b) How many males have blue eyes?

Blue eyes = filled squares.

Generation I: none (male 1 is empty)

Generation II:
- Male 3 (filled), Male 4 (filled) → 2

Generation III:
- Male 3 (filled), Male 4 (filled), Male 5 (filled) → 3

Total = 2 + 3 = 5

✔ Answer: 5

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Question 2:

a) How many females are shown in this pedigree?

Look for all circles:

Generation I:
- Female 2 → 1 female

Generation II:
- Female 2, Female 5 → 2 females

Generation III:
- Female 2, Female 6 → 2 females

Total females = 1 + 2 + 2 = 5

✔ Answer: 5

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b) How many females have blue eyes?

Blue eyes = filled circles.

Generation I: Female 2 → filled → 1

Generation II: Female 5 → filled → 1

Generation III: Female 6 → filled → 1

Female 2 in Gen II and Female 2 in Gen III are empty → not blue eyes.

Total = 1 + 1 + 1 = 3

✔ Answer: 3

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Question 3:

How many marriages are shown in this pedigree?

Marriages = horizontal lines connecting a square and a circle.

Generation I:
- Male 1 — Female 2 → 1 marriage

Generation II:
- Male 1 — Female 2 → 1 marriage
- Male 4 — Female 5 → 1 marriage

Total = 1 + 1 + 1 = 3

✔ Answer: 3

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Question 4:

What is the genotype of the father in the first generation?

Father in first generation = Male 1 (square, empty → brown eyes)

He married Female 2 (filled → blue eyes → genotype bb)

They had children:

- Female 2 (empty → brown eyes)
- Male 3 (filled → blue eyes → bb)
- Male 4 (filled → blue eyes → bb)

Since Male 3 and Male 4 have blue eyes (bb), they must have gotten one b from mom and one b from dad.

Mom is bb, so she gave them b.

So dad must have given them b too → meaning dad has at least one b.

But dad has brown eyes → so he must have at least one B.

Therefore, his genotype must be Bb.

✔ Answer: Bb

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Final Answer:
1. a) 8
b) 5
2. a) 5
b) 3
3. 3
4. Bb