Genetics Flashcards
What is domestication?
Involves many processes over thousands of years with very specific
changes
Many define it as animals who adapted to be close to humans and their reproduction controlled by humans
“animals around the house”
What things are necessary for domestication?
Diet
Growth rate
Reproduce easily in captivity
Disposition/Temperament (flight or fight reduced)
Social structure
What changes first during domestication?
early decrease in size, later increase (mammals)
early increase in size (birds)
decreased flight distance from people
coat and plumage color changes (this relates to behavior)
retention of neotenic characters
decrease in cranial capacity
increased genetic variability,
increased rate of increase in variability
Domestication is driven by…
Humans and their needs
Adaptations to the Human environment
mobility, water, grazing, disease, predation, storms/weather
Adaptations to Human need
Beasts of burden (castration, confinement, sacrifice, etc)
Control Reproduction (and genetic variability)
Slow Reproduction
Fast Reproduction
Domesticated animals fall into what 3 categories?
Breed (standard or gentrified)
Industry stock
Landrace
General process from domestication to industrial breed
Domestication occurs
Become landrace/ primitive breed (adapting to environment) (not yet a true breed)
Becomes standard breed as genetic variability gets smaller
Becomes industrial breed with small genetic variability
Single gene traits can be classified as…
Autosomal dominant (rare in vetmed)
Autosomal recessive
Penetrance
Autosomal Dominant traits
Rare in Veterinary Medicine!
Both males and females are equally affected as the gene is located on a non-sex linked chromosome
Requires 1 copy of the affected genet to cause disease
* Mutant/Normal (M/N) * Mutant/Mutant (M/M)
Examples:
* Polycystic Kidney Disease in Persian Cats
* Progressive Rod/Cone Degeneration/Atrophy in English Mastiffs and Bullmastiffs
Autosomal Recessive traits
What we encounter commonly
Must obtain one of each gene from
each parent
Requires 2 copies of the affected genes to express disease
* Normal
- Normal/Normal(N/N)
* Carrier
- Mutant/Normal(M/N)
* Affected
-Mutant/Mutant (M/M)
Example: Congenital Myasthenia Gravis of Smooth Fox Terriers or other breeds with PRCD
Penetrance is based on a probability calculation of…
Number of individuals with the affected genotype that express the phenotype
Follows the same rules are dominant and recessive but it can be complete or incomplete
Complete penetrance
100% will have the disease (all individuals with a particular genotype express disease)
Example: MG of Smooth Fox Terriers
Incomplete Penetrance
Only some with the genotype will express the disease (phenotype)
Example: Hereditary Cataracts of Australian Shepherds
The “At risk” calculation is tied to ____________.
Pentrance
Recessive requires 2 copies AND does it have complete or incomplete
expression?
Hence the “at risk” calculation that a vet or breeder needs to consider
The “At risk” calculation should be considered prior to…
Breeding
Polygenetic Traits definition
Multiple genes involved
* This requires genomic sequencing of affected and non-affected animals
* Largely depends on statistics
* Multiple outside influences that affect the expression of the phenotype
