Genetics Flashcards
Genotype
genetic makup of a individual
Heterozygous
have 2 different forms of a gene for specific trait/dz
Homozygous
have 2 identical forms of a gene for specific trait/dz
Penetrance
proportion of genetically affected individuals that express a trait + extent that trait is present
o = likelihood that a given gene will result in dz
o Incomplete suggest <100%
Phenotype
observable characteristics resulting from interaction of genetic makeup and environment
Polygenic
trait/dz caused by 2 or > genes
Autosomal recessive
- Carried on autosomal chromosome
- Both copies of mutation have to be present
Pedigree evaluation autosomal recessive
o Skips generations → parents can be asymptomatic carriers
o No sex predilection
o Mating of silent carriers (heterozygotes) parents → 25% affected phenotype, 75% not
o Mating of 2 affected parents → 100% affected offspring
Autosomal dominant
- Only 1 copy of mutation necessary for clinical phenotype
o Homozygote or heterozygote
Predigree eval Autosomal dominant
o At least 1 affected parent
Heterozygous → 50% affected offspring
Homozygous → 100% affected offspring
o No sex predilection
X-linked
- Gene carried on X chromosome
- Most commonly recessive
o Males almost always show phenotype since only 1 X
o Females can be silent carriers unless both X’s carry mutation
Pedigree eval X linked
o Affected males > females
o Affected males crossed w normal female → silent (unaffected) females
o Silent carrier females pass the trait to 50% male offspring
o Affected male crossed w silent carrier female → can result in affected female
Uncommon
Polygenic
- 2 or > genes working together to develop a specific trait
- Many inherited dz in vetmed
Incomplete penetrance
- <100% of individuals with mutation will have clinical trait/dz
- Variable expressivity of trait → severity of phenotypic expression
Which diseases are proven heritable?
Endomyocardial fibrosis
ASD
PDA
PS
SAS
TOF
TVD
VSD
Breeds endomyocardial fibrosis
Siamese
Burmese
Colony of DSH
Pattern of inheritance endomyocardial fibrosis
Unknown
What is endomyocardial fibrosis
Rare feline CHD
* LA and LV dilation
* Severe endocardial thickening
ASD breeds
Boxers
Doberman
Samoyed
Standard Poodles
ASD pattern of inheritance
Autosomal dominant more likely
ASD pedigree studies
- Pedigree evaluation performed in Poodle and Doberman
- Ostium secondum defect for both
- Hu: 2 transcription factors identified
- GAT4A and NKC2.5
- Not identified in dogs
PDA breeds
Poodle
PDA pattern of inheritance
Polygenic
PS breeds
Scottish Terriers
Wire-haired terriers
Miniature schnauzers
Beagles
PS pattern of inheritance
Polygenic
PS studies genetics
- Only studied in Beagles
- Specific gene mutation not identified
SAS breeds
Newfounland
Golden retreivers
Rottweiler
SAS pattern of inheritance
Polygenic
SAS studies genetics
Mostly studied in Newfoundland
TOF breeds
Keeshond
TOF pattern of inheritance
Polygenic
TOF studies genetics
- Spectrum of defects
- Genetic linkage to 3 canine chromosomes
- Hu: conotruncal defects
- Zinc finger protein multitype 2 (ZFPM2)
- Modulator of GATA transcription factor
TVD breeds
Labs
TVD pattern of inheritance
Autosomal dominant with reduced penetrance
TVD genetic studies
Linked to an area on chromosome 9
No specific gene mutation identified
VSD breeds
Lakeland Terriers
WHWT
English Spinger Spaniel
Basset Hounds
Beagle
VSD pattern of inheritance
Autosomal recessive
(beagles)
Autosomal dominant w incomp. penetrance OR polygenic (Springer Spaniels)
Gene for ARVC
Striatin gene
