Pedigree worksheet illustrating a family tree with information on hemophilia inheritance, including symbols for males, females, and affected individuals.

Here are the answers to the questions on the pedigree worksheet, based on the rules of sex-linked inheritance provided in the text.

1. Number all individuals on the pedigree at the top of each shape.
*(Note: This is an instruction for you to do on your paper. Start with 1 and 2 in Generation I, then 3, 4, 5 in Generation II, and so on, moving left to right.)*

2. Males (Squares)
* a. How many males are there?
Count every square in the diagram (Generations I through IV).
* Gen I: 1 male
* Gen II: 2 males
* Gen III: 3 males
* Gen IV: 6 males
* Total: $1 + 2 + 3 + 6 = 12$
Answer: 12

* b. How many males have hemophilia?
Count the shaded (darkened) squares.
* Gen IV has 2 shaded squares. No other generations have shaded squares.
Answer: 2

3. Females (Circles)
* a. How many females are there?
Count every circle in the diagram.
* Gen I: 1 female
* Gen II: 1 female
* Gen III: 2 females
* Gen IV: 4 females
* Total: $1 + 1 + 2 + 4 = 8$
Answer: 8

* b. How many females have hemophilia?
Count the shaded (darkened) circles.
* Gen I has 1 shaded circle (Individual #2).
* Gen IV has 1 shaded circle.
Answer: 2

4. Marriages
* How many marriages are there?
Count the horizontal lines connecting a square and a circle.
* Couple in Gen I.
* Couple in Gen II.
* Couple in Gen III.
Answer: 3

5. Offspring Lines
* a. How many children did the first couple (couple in row I) have?
Follow the vertical line down from the marriage in Generation I. It connects to a bracket holding Individuals #3, #4, and #5 in Generation II.
Answer: 3

* b. How many children did the third couple (couple in row III) have?
Follow the vertical line down from the marriage in Generation III. It connects to a bracket holding 6 individuals in Generation IV.
Answer: 6

6. Generations
* a. How many generations are there?
Count the Roman numerals on the left side (I, II, III, IV).
Answer: 4

* b. How many members are there in the fourth generation?
Count all shapes in Row IV. There are 4 males and 4 females.
Answer: 8

7. Genotypes of Males
*Rule: Males are XY. Normal clotting is dominant ($X^N$), Hemophilia is recessive ($X^n$).*

* a. What is the genotype for Individual #1? Phenotype?
Individual #1 is a clear square (normal male). He must have the dominant allele.
Genotype: $X^N Y$
Phenotype: Normal blood clotting

* b. What is the genotype for Individual #10? Phenotype?
*(Assuming standard numbering where Gen IV starts at #9, Individual #10 is the second child in Gen IV).*
Individual #10 is a clear square (normal male).
Genotype: $X^N Y$
Phenotype: Normal blood clotting

* c. What is the genotype for the first born male in generation III? Phenotype?
The first born male in Gen III is Individual #5. He is a clear square (normal).
Genotype: $X^N Y$
Phenotype: Normal blood clotting

8. Females with Hemophilia
* a. How many females have the genotype $X^n X^n$?
Females with hemophilia must have two recessive alleles (shaded circles). We counted 2 shaded circles in Question 3b.
Answer: 2

9. Carrier Females
* a. What would be the genotype for the female who marries into the family in generation III?
Let's look at the parents of the affected children in Generation IV.
The father in Generation III (Individual #5) is normal ($X^N Y$).
They have a daughter with hemophilia ($X^n X^n$) in Generation IV.
For a daughter to be $X^n X^n$, she must get one $X^n$ from her dad and one $X^n$ from her mom.
Since the dad gave an $X^n$ (wait, the dad is normal $X^N Y$, he gives $X^N$ to daughters)...

*Correction:* Let's re-read the chart carefully.
In Generation III, the male (#5) is normal ($X^N Y$). The female who married in is clear (normal phenotype).
They have a son with hemophilia ($X^n Y$) and a daughter with hemophilia ($X^n X^n$) in Generation IV.

Actually, looking at Generation IV:
- There is a shaded square (hemophiliac male, $X^n Y$). His Y came from his dad. His $X^n$ came from his mom. So the mom carries the gene.
- There is a shaded circle (hemophiliac female, $X^n X^n$). One $X^n$ came from her dad, and one $X^n$ came from her mom.

Wait, if the daughter in Gen IV is hemophiliac ($X^n X^n$), her father (Male #5 in Gen III) must have given her an $X^n$. This means Male #5 must have hemophilia. But Male #5 is drawn as a clear square (normal).

*Let's re-examine the image logic:*
Usually, in these problems, if a child has a trait the parent doesn't show, it's recessive.
If the daughter in Gen IV is affected ($X^n X^n$), the father MUST be affected ($X^n Y$). But he is drawn normal.

*Alternative interpretation:* Is it possible the question implies the female marrying in is a carrier?
Let's look at the son in Gen IV (shaded square, $X^n Y$). He got Y from Dad. He got $X^n$ from Mom. So Mom is at least a carrier ($X^N X^n$ or $X^n X^n$).
Since the Mom is drawn as a clear circle, she is phenotypically normal. Therefore, she must be a carrier.

So, the female who married into the family in Generation III is a carrier.
Answer: $X^N X^n$