1. Journal Entry
Why are sex-linked recessive traits such as red-green colour-blindness and hemophilia more commonly found in males than in females? Explain your answer in terms of the X chromosome.

2. Pedigrees
A table to explain how sex-linked traits are passed along

3. Constructing a Pedigree
Female
Male

4. Connecting Pedigree Symbols
Examples of connected symbols:
Fraternal twins
Identical twins

5. Connecting Pedigree Symbols
Examples of connected symbols:
Married Couple
Siblings

6. Pedigree uses:
autosomal dominant conditions (e.g.Huntington disease, polydactyly)
autosomal recessive conditions (e.g., cystic fibrosis, Tay-Sachs disease, attached earlobes)
sex-linked recessive conditions (e.g., colour-blindness, Duchenne muscular dystrophy, hemophilia)

8. What they tell us Pedigrees will display phenotypes and gender
Genotypes can only be determined using logic!

9. Problem 1

10. Problem 2

11. 1. How many generations are represented in the chart for sickle-cell anemia? __________
2. How many carriers of the sickle-cell trait are in each generation? _________________
3. How many people in the family were born with sickle-cell anemia? _______________
4. From with parent did the second-generation children inherit the sickle-cell gene? ____
5. In which generation did sickle-cell anemia first show? __________________________