Lecture 4 - Companion Animals Flashcards
What is linkage disequilibrium
Non-random association of alleles at two or more loci on the same DNA strand
Alleles from different genes next to each other tend to be inherited together
What is pleiotropy
When one gene influences two or more (often seemingly unrelated traits) ie - arm length and leg length (same genes, different traits)
Linkage disequilibrium and pleiotropic genes can lead to the non-independence of
Breeding values for different (and often seemingly unrelated) traits
What is genetic correlation
The correlation between the genetic influences on a trait and the genetic influences on a different trait
What is the range of genetic correlation
-1 to 1
A genetic correlation of 1 implies that
Genetic influences on 2 traits are identical
A genetic correlation of 0 implies that
Genetic influences on 2 traits are independent
A genetic correlation of -1 implies that
Genetic influences on 2 traits have opposite effects
Genetic correlations are important because selection on one trait can lead to the
Evolution of genetically correlated (and often seemingly unrelated) traits. This is called indirect selection
Example of indirect selection
Selection for increased yearling weight in cattle could possibly lead to a correlated increase in dystocia
In animal breeding, the response of multiple genetically correlated traits to selection is predicted using the
Multivariate breeder’s equation which requires estimates of heritability as well as genetic correlations
Involving multiple traits simultaneously is done through
Index Selection
Genetic correlations can be exploited to
Improve hard to measure traits by selecting on a more easily measured one
Example of using genetic correlations to improve hard to measure traits by selecting on an easier to measure one
Selecting for sheep with rumen bacterial community (easy to measure) that is correlated with methane emissions (hard to measure)
Genomes are useful for
Understanding evolution
Animal health and welfare
Models of human disease
What was the first species we domesticated
Dogs (20 000 - 40 000 years ago)
What are breed standards
A set of morphological measures set by a fancier club that define the critical characteristics of a breed
Problems with breeds (ie the breed barrier)
A dog may only be registered if both sire and dam are registered
Reproductive isolation (inbreeding & receives no new genetics)
What is the world’s oldest/rarest breed
Xoloizcuintli
What are dogs an example of
Very rapid evolution
Unintended genetic consequences of breeds and breed standard - most breeds went though a
genetic bottleneck when they were formed
Small populations continuously lose genetic diversity because of
Genetic drift (changes in allele frequencies due to random sampling (by chance & eventually allele disappears)
Mating among relatives (inbreeding) increases
Homozygosity, and as a consequence, the expression of recessive deleterious mutations.
Inbreeding depression
Reduction of fitness in inbred individuals is known as inbreeding depression
Selection on breed standard traits can indirectly select for
Seemingly unrelated unhealthy phenotypes
Intense selection on specific traits/genes can increase
Frequency of deleterious alleles at linked genes
Inbreeding depression causes what in golden retrievers
Reduced fecundity
Health issues in dogs - examples
Obesity, retinal detachments, keratin, hip dysplasia, deafness, urolithiasis, brachycephalic syndrome, hip & elbow dysplasia
In a study with inherited defects in pedigree dogs with disorders related to breed standards, what did they find
84 disorders directly or indirectly associated with conformation
Each of the top 50 breeds was found to have at least one aspect of its conformation predisposing it to a disorder
In a study looking at inherited defects in pedigree dogs with disorders not related to breed standards, what did they find?
Most commonly reported mode of inheritance was autosomal recessive (71%) - probably genetic drift
Most commonly affected body system was nervous sensory system
A genome-wide association study identifies a novel _______ locus in dogs
Glaucoma
Did a GWAS
Considerations about pet DNA tests
Not regulated
False positives are possible
Some tests/mutations are propriety
Variable assistance with interpretation of results
Ancestry can only be attributed to breeds present in the database
Results for quantitative traits are harder to interpret
Applications of genetics in wildlife veterinary science
Detection of pathogens/diagnostic
Disease etiology/genetic basis of disease
Zoonoses, public health
Conservation genetics applies genetic tools and data to promote
The conservation of biodiversity, including endangered wildlife and livestock breeds
Conservation genetics purposes
Limit losses of genetic diversity and adaptive potential - promote genetic variation
Limit genetic disorders and inbreeding depression
Limit spread and/or impacts of pathogens
In situ vs ex situ conservation genetics
In situ - characterize genetic diversity in free-living populations
Ex-situ - maintain genetic diversity and limit inbreeding in captive breeding programs
In in situ conservation genetics, when you characterize genetic diversity, what do you do
Identify genetically unique/isolated populations
Identify populations with low genetic diversity
Quantify h2 for resistance to new diseases
Quantify inbreeding depression
In in situ conservation genetics, when you inform translocations, what do you do
- Balance risk of inbreeding vs outbreeding depression
- Prevent or mitigate pathogen transmission
- Identify individuals/populations to initiative/supplement captive breeding programs
- Monitor breeding success of reintroduced individuals
In ex-situ conservation genetics, how do you maintain genetic diversity and limit inbreeding?
- Parentage analyses, and genomic diversity
- Manage reintroduction efforts
Canadian example of conservation genetics
Vancouver island marmot
Have heart issues so limited life expectancy
Why should zoos adopt genomics
- Zoos preserve genetic diversity in endangered species and limit inbreeding in captive populations
- Genomic estimates help minimize inbreeding and inbreeding depression
- Genomics can be used to selectively remove unwanted DNA from captive populations
- Can identify deleterious recessive alleles and remove them from the population through marker assisted selection or editing
- Can identify individuals most suited for release in the wild
