Pedigree charts worksheet - Free Printable

Problem Analysis:

The worksheet focuses on understanding pedigrees and the inheritance of a recessive genetic trait, albinism, in humans. Albinism is caused by a recessive allele (`a`), while the dominant allele (`A`) results in a normal phenotype. The genotypes and their corresponding phenotypes are as follows:
- AA: Normal (homozygous dominant)
- Aa: Normal (heterozygous carrier)
- aa: Albino (homozygous recessive)

We will solve each part of the worksheet step by step.

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Part 1: Genotypes and Phenotypes

#### Given:
- AA: Normal
- Aa: Normal
- aa: Albino

#### Pedigree Analysis:
The pedigree shows:
- A couple with one child.
- The child is shaded gray, indicating they have albinism (`aa`).

#### Questions:
1. How many children does the couple have?
- The pedigree shows one child.

2. What is the sex of the oldest child?
- The child is represented by a circle, which indicates a female.

3. How many grandchildren does the couple have?
- The couple has no grandchildren shown in this pedigree.

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Part 2: Fill Out the Blanks of the Pedigree

#### Pedigree Analysis:
The second pedigree shows:
- An original couple with two children.
- One child is shaded gray (albino).
- The other child has two children, one of whom is shaded gray (albino).

#### Step-by-Step Solution:

1. Determine the Genotypes of the Original Couple:
- Both parents must be carriers (`Aa`) because:
- They have a child with albinism (`aa`).
- For a child to inherit `aa`, both parents must contribute an `a` allele.

2. Determine the Genotypes of the Children:
- Child 1 (Shaded Gray): This child is albino (`aa`).
- Child 2 (Unshaded): This child is normal but could be either `AA` or `Aa`. Since one of their offspring is albino, this child must be a carrier (`Aa`).

3. Determine the Genotypes of the Grandchildren:
- Grandchild 1 (Shaded Gray): This grandchild is albino (`aa`).
- Grandchild 2 (Unshaded): This grandchild is normal (`AA` or `Aa`). Since the parent is `Aa`, this grandchild could be either `AA` or `Aa`.

#### Questions:
a) How many children did the original couple have?
- The original couple had two children.

b) How many grandchildren do they have?
- The original couple has three grandchildren (two from Child 2 and one from Child 1).

c) How many of their grandchildren are albino?
- Two of the grandchildren are albino (`aa`).

d) Create an extension to the pedigree to show the albino granddaughter marrying and having a son who is NOT albino.
- The albino granddaughter (`aa`) marries someone who is not albino. For their son to be normal, the partner must be at least a carrier (`Aa`).
- Possible genotypes for the son:
- If the partner is `AA`: Son = `Aa` (normal)
- If the partner is `Aa`: Son = `Aa` (normal) or `aa` (albino, but we need normal, so `Aa` is correct).

#### Extended Pedigree:
- Albino granddaughter (`aa`) marries a carrier (`Aa`).
- Their son is `Aa` (normal).

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Final Answers:

#### Part 1:
1. How many children does the couple have?
Answer: 1
2. What is the sex of the oldest child?
Answer: Female
3. How many grandchildren does the couple have?
Answer: 0

#### Part 2:
a) How many children did the original couple have?
Answer: 2
b) How many grandchildren do they have?
Answer: 3
c) How many of their grandchildren are albino?
Answer: 2
d) Extended Pedigree:
- Albino granddaughter (`aa`) marries a carrier (`Aa`).
- Their son is `Aa` (normal).

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Boxed Final Answer:

\[
\boxed{
\text{Part 1: 1, Female, 0} \\
\text{Part 2: 2, 3, 2}
}
\]