Transcript Pedigrees

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
Is III-4 a male or female?
Is II-5 affected or unaffected?
Draw and label this one!
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?