This document is a family pedigree studying color blindness. It shows that the father and one sister have color blindness, while the mother and other sister do not. The colorblind sister has two colorblind sons but her daughter has normal vision. The narrator has one normal son and daughter. It is stated that color blindness is a sex-linked trait, as the allele is on the X chromosome.

1. Family pedigree
Study of a phenotype in a family
Prof. Beatriz Duro
Colegio Internacional SEK Ciudalcampo

2. Family Pedigree Symbols

3. Woman that does not show
the studied phenotype
Man that does not show
the studied phenotype.
Woman that shows the
studied phenotype.
Man that shows the
studied phenotype.
Phenotype studied: Haemophilia
I
II
III
IV
1 2
1
1
1
2
2
2 3
3
3
4
4
5

4. Phenotype studied:
Color blindness
"My mother and my older sister can perfectly distinguish colors, but my father and my sister Julie have
the same problem as I do. Julie has 2 colorblind sons, yet her only daughter has perfectly normal vision. I
have a son and a daughter who both have normal vision, like their mother. Although my mother has
normal vision, her brother had the same problem I have."

5. p. 57
El daltonismo es un carácter que se hereda ligado al
sexo. ¿Qué datos apoyan esta afirmación?
El alelo responsable del daltonismo es
dominante o recesivo?
II
III
IV
I
1 2
1
1
1
2
2
2 3
3
3
4
4 5
5
Phenotype studied: Color blindness