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Population genetics: Companion animals - Coggle Diagram
Population genetics: Companion animals
"Mendelian" single gene disease
Complex disease continuous
natural evolution driven by survival
early artificial evolution driven by function
later artificial evolution driven by body shape
loss of genetic diversity
inbreeding
genetic drift
gain of genetic diversity
immigration
mutation
only exists at population level
artificial selection can lead to disease
"directed" selection related to exaggerated features
"undirected" selection can lead to things like deafness
Extreme conformation in dogs= altered so much away from ancestral natural appearance that they commonly suffer from poor health + welfare
can use artificial selection to reduce frequency of some specific disorders
simple (PRA, PLL. CLAD, copper toxicosis): molecular genotyping
mutations at one gene
blood/mouth swabs
DNA screening
microchip/tattoo number, KC registered name/number
identify clear, carrier, affected
complex (HD, ED, epilepsy, bloat)
Breeding advice
autosomal-recessive conditions (majority)
clear= clinically normal, can mate with any dog
carrier= clinically normal, only mate with clear dogs
affected= clinically affected, only mate with clear dogs
autosomal-dominant conditions
clear= clinically normal, mate with any
heterozygous affected= clinically affected, don't breed
homozygous affected= clinically affected, don't breed
linkage tests can't find exact gene but knows where it is approx in genome, not as accurate
Hip dysplasia
soft tissue laxity
abnormal forces during weight bearing
osteoarthritis + lameness
Estimated Breeding Values (EBV)
from phenotype
weighting to maximise accuracy of selection
select for positive + against negative
Coefficient of inbreeding (COI)
probability that 2 copies of gene at a locus are Identical by Descent (IBD)
rule: 0.5 x relationship between parents
symbol: F
reflection of reduced proportion of heterozygosity
Relationship and Inbreeding
mating of relatives= common ancestor (IBD)
can lead to specific inherited disease
can lead to inbreeding depression
many harmful recessive genes lethal: increased embryonic death + stillbirths
less severe recessive genes: decreased production + reproductivity
= any locus where heterozygote performance > average of homozygote
Hybrid vigour= superior average performance of crossbred progeny compared with the average of their purebred parent species
Solutions
aim to constrain COI to <5% per generation
minimise conancestry of matings
increase number of animals used for breeding
equalise use of males and females
outcrossing (crossing between breeds)