Types of Pedigree

Genotype vs. Phenotype

There are two kinds of pedigree
charts.

1. Genotype pedigree
2. Phenotype pedigree

genotype pedigree

phenotype pedigree

Multiple Choice

What is the definition of phenotype?

• The physical trait someone shows based on their genotype

• A code made of two alleles for a given trait

• How someone feels is shown in their brain patterns.

• HOMOZYGOUS!

Multiple Choice

What is the definition of genotype?

• The physical trait someone shows based on their genotype

• How someone feels is shown in their brain patterns.

• A code made of two alleles for a given trait

• HETEROZYGOUS!

Genotype pedigrees can have half-shaded circles and boxes. A half-shaded shape means an individual is heterozygous. ​They have one copy of each allele for a trait.

Individuals with two copies of the allele are fully shaded.

​

​

​= Heterozygous

​

​= Homozygous

Multiple Choice

True or False. Individuals that are heterozygous are half-shaded circle or squares.

• True

• False

Individuals who do not have the allele are clear (no shading). Genotype charts record the alleles in a particular family.

​

​= Homozygous

Genotype Pedigrees will tell you what trait is being looked for.

Phenotype pedigrees only have
shaded and clear circles and boxes.
Shaded boxes show that the trait is
visible. Phenotype charts record
when a trait appears in a particular
family.

​

​= Visible

​

​= Not Visible

Multiple Choice

In phenotype pedigree charts a fully shaded circle or square means what?

• Visible

• Not Visible

• Heterozygous

• Homozygous

What is the purpose of a phenotype pedigree?
Phenotype pedigrees are useful when a scientist is trying to figure out if a trait is dominant or recessive.

When a trait is visible, but nothing is known about the genetics, there are three possibilities:
1. Homozygous recessive
2. Heterozygous
3. Homozygous dominant

These ALL show as shaded on a phenotype pedigree

Multiple Choice

True or False. You can tell the exact genotype of an individual based on a phenotype pedigree chart.

• True

• False

Analyzing the patterns in the pedigree chart can show if the trait is recessive or a dominant.
Recessive patterns: Recessive traits can “skip” generations, so shaded individuals might not have a shaded parent.

​However, two shaded partners will always have 100% shaded offspring.

Multiple Choice

How can you tell if a trait is recessive on a pedigree chart?

• The trait will skip generations

• The trait will show up in every generation

Dominant patterns: Shaded individuals will always have at least one shaded parent. Two shaded partners might have both shaded and
clear offspring.

Multiple Choice

True or False. When tracking a dominant trait in a pedigree, a shaded individual will have at least one shaded parent.

• True

• False

Uncertain patterns: Sometimes pedigrees do not have enough information to be sure.