Pedigrees

• Pedigree – “family tree” showing traits or diseases

• Standard Symbols:

male female

(shaded) has trait or disease

(half shaded) known carrier

(not shaded) does not have trait or disease

deceased

Mating or married parents

children

Other Symbols

Skkiiirrttt! This is one messed up pedigree!

How to Label a Pedigree

Draw and label this one!

Is III-4 a male or female?

Is II-5 affected or unaffected?

How to Determine Inheritance Pattern

1. If trait or disease shows up in all generations, it is probably dominant.

2. If the trait or disease usually skips generations, it is probably recessive.

3. If carriers are shown, or if a child has it and both parents do not, it is DEFINITELY recessive.

Determining Genotypes from Pedigrees

• Dominant Traits (ex. tongue rolling)

• Recessive Traits (cystic fibrosis)

Test Crosses

• Test-cross – method used by breeders to determine the genotype of an animal– Mate the individual with an unknown genotype

with one that you know for sure (HOMOZYGOUS RECESSIVE)

– Based on the results, you will know the unknown animal!

Example

• Dwarfism in dogs is a recessive trait– NN __________– Nn __________– nn __________

Example Problem:

• You mate your normal-sized dog with a dwarf dog. The litter turns out to be all normal-sized. Was the genotype of your dog NN or Nn?