Lecture 4 - Companion Animals

Question 1

What is linkage disequilibrium

Answer 1

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

Question 2

What is pleiotropy

Answer 2

When one gene influences two or more (often seemingly unrelated traits) ie - arm length and leg length (same genes, different traits)

Question 3

Linkage disequilibrium and pleiotropic genes can lead to the non-independence of

Answer 3

Breeding values for different (and often seemingly unrelated) traits

Question 4

What is genetic correlation

Answer 4

The correlation between the genetic influences on a trait and the genetic influences on a different trait

Question 5

What is the range of genetic correlation

Answer 5

-1 to 1

Question 6

A genetic correlation of 1 implies that

Answer 6

Genetic influences on 2 traits are identical

Question 7

A genetic correlation of 0 implies that

Answer 7

Genetic influences on 2 traits are independent

Question 8

A genetic correlation of -1 implies that

Answer 8

Genetic influences on 2 traits have opposite effects

Question 9

Genetic correlations are important because selection on one trait can lead to the

Answer 9

Evolution of genetically correlated (and often seemingly unrelated) traits. This is called indirect selection

Question 10

Example of indirect selection

Answer 10

Selection for increased yearling weight in cattle could possibly lead to a correlated increase in dystocia

Question 11

In animal breeding, the response of multiple genetically correlated traits to selection is predicted using the

Answer 11

Multivariate breeder’s equation which requires estimates of heritability as well as genetic correlations

Question 12

Involving multiple traits simultaneously is done through

Answer 12

Index Selection

Question 13

Genetic correlations can be exploited to

Answer 13

Improve hard to measure traits by selecting on a more easily measured one

Question 14

Example of using genetic correlations to improve hard to measure traits by selecting on an easier to measure one

Answer 14

Selecting for sheep with rumen bacterial community (easy to measure) that is correlated with methane emissions (hard to measure)

Question 15

Genomes are useful for

Answer 15

Understanding evolution
Animal health and welfare
Models of human disease

Question 16

What was the first species we domesticated

Answer 16

Dogs (20 000 - 40 000 years ago)

Question 17

What are breed standards

Answer 17

A set of morphological measures set by a fancier club that define the critical characteristics of a breed

Question 18

Problems with breeds (ie the breed barrier)

Answer 18

A dog may only be registered if both sire and dam are registered
Reproductive isolation (inbreeding & receives no new genetics)

Question 19

What is the world’s oldest/rarest breed

Answer 19

Xoloizcuintli

Question 20

What are dogs an example of

Answer 20

Very rapid evolution

Question 21

Unintended genetic consequences of breeds and breed standard - most breeds went though a

Answer 21

genetic bottleneck when they were formed

Question 22

Small populations continuously lose genetic diversity because of

Answer 22

Genetic drift (changes in allele frequencies due to random sampling (by chance & eventually allele disappears)

Question 23

Mating among relatives (inbreeding) increases

Answer 23

Homozygosity, and as a consequence, the expression of recessive deleterious mutations.

Question 24

Inbreeding depression

Answer 24

Reduction of fitness in inbred individuals is known as inbreeding depression

Question 25

Selection on breed standard traits can indirectly select for

Answer 25

Seemingly unrelated unhealthy phenotypes

Question 26

Intense selection on specific traits/genes can increase

Answer 26

Frequency of deleterious alleles at linked genes

Question 27

Inbreeding depression causes what in golden retrievers

Answer 27

Reduced fecundity

Question 28

Health issues in dogs - examples

Answer 28

Obesity, retinal detachments, keratin, hip dysplasia, deafness, urolithiasis, brachycephalic syndrome, hip & elbow dysplasia

Question 29

In a study with inherited defects in pedigree dogs with disorders related to breed standards, what did they find

Answer 29

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

Question 30

In a study looking at inherited defects in pedigree dogs with disorders not related to breed standards, what did they find?

Answer 30

Most commonly reported mode of inheritance was autosomal recessive (71%) - probably genetic drift
Most commonly affected body system was nervous sensory system

Question 31

A genome-wide association study identifies a novel _______ locus in dogs

Answer 31

Glaucoma
Did a GWAS

Question 32

Considerations about pet DNA tests

Answer 32

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

Question 33

Applications of genetics in wildlife veterinary science

Answer 33

Detection of pathogens/diagnostic
Disease etiology/genetic basis of disease
Zoonoses, public health

Question 34

Conservation genetics applies genetic tools and data to promote

Answer 34

The conservation of biodiversity, including endangered wildlife and livestock breeds

Question 35

Conservation genetics purposes

Answer 35

Limit losses of genetic diversity and adaptive potential - promote genetic variation
Limit genetic disorders and inbreeding depression
Limit spread and/or impacts of pathogens

Question 36

In situ vs ex situ conservation genetics

Answer 36

In situ - characterize genetic diversity in free-living populations
Ex-situ - maintain genetic diversity and limit inbreeding in captive breeding programs

Question 37

In in situ conservation genetics, when you characterize genetic diversity, what do you do

Answer 37

Identify genetically unique/isolated populations
Identify populations with low genetic diversity
Quantify h2 for resistance to new diseases
Quantify inbreeding depression

Question 38

In in situ conservation genetics, when you inform translocations, what do you do

Answer 38

• 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

Question 39

In ex-situ conservation genetics, how do you maintain genetic diversity and limit inbreeding?

Answer 39

• Parentage analyses, and genomic diversity
• Manage reintroduction efforts

Question 40

Canadian example of conservation genetics

Answer 40

Vancouver island marmot
Have heart issues so limited life expectancy

Question 41

Why should zoos adopt genomics

Answer 41

• 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