1. Pedigrees

3. What are pedigree charts?

4. A pedigree for any family, be it dogs, cats or humans, shows the pattern of inheritance in a family for a specific trait. Males are shown as squares and females are shown as circles. = =

5. Each generation is shown as a Roman numeral and each person in a generation is numbered. The trait that is being expressed is shown as a shaded shape.

6. So, here we know that individual I1 is a male that shows the trait.
His daughter, II1, also shows the trait.
His sons, II2 and II3, do not show the trait.

7. Let’s do this together... I II six III IV
Observe the pedigree. Number the generations and each person on the pedigree.
In this family, how many individuals show the trait?
Which males show the trait? (generation,number) I 1 2 II
six 4 1 2 3 5
III 1 2 3 4 5
II-5
III-2
III-3
IV-1 IV 1 2

8. Determining genotypes
Start with what you know.
In this case,
N = normal feet
n = webbed feet
Since shaded show the trait, all shaded are homozygous recessive.
And all unshaded have at least one dominant gene. N nn N nn N N nn N nn nn N N nn N

9. Determining genotypes
Looking at individual IV-1 and his parents.
In order for him to be “nn”, he had to have inherited his recessive genes from his parents, since his parents don’t show the recessive trait, they both have to be _____?
Write it down. N nn N nn N N nn N nn nn N n N n Nn
heterozygous nn N

10. Determining genotypes
Keep working up that way. N n nn
What is the only possible genotype for II-4?
What is the only possible genotype for I-1? N n nn N n N n nn N n nn nn Nn Nn
This means that the rest are also... nn N

11. Determining genotypes
Keep working up that way.
Can you determine the genotype of individual IV-2? Nn nn Nn nn Nn Nn nn Nn nn nn Nn Nn
No, he can be either NN or Nn.
(answer key: nn N

12. Work with a partner
Answer the rest of your sheet with a partner.