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BVetMed3 POS - Integrated Applied Science > Population Genetics In Companion Animals > Flashcards

Population Genetics In Companion Animals Flashcards

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Biology 101 flashcards
1
Q

How many chromosomes do dogs have?

A

78

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2
Q

How many chromosomes do cats have?

A

38

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3
Q

How many chromosomes do rabbits have?

A

44

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4
Q

How does the number of genes relate to the number of chromosomes as chromosome number varies between species?

A

Roughly the same number of genes

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5
Q

What does the founder effect mean?

A

New colony started by a few members of original population

Not all genes from original population present for repopulation:

  • reduced genetic variation
  • non-random sample of genes from original population
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6
Q

What is a genetic bottleneck?

A

Occur when a populations size is reduced for at least one generation

Reduced genetic diversity

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7
Q

What are the types of simple/Mendelian inheritance?

A

Autosomal dominant
Autosomal recessive
X-linked dominant
X-linked recessive

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8
Q

What are the broad categories of inheritance?

A

Simple
Complex
Selection:natural or artificial

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9
Q

What is the difference between simple and complex inheritance?

A

Genes interact with each other

Can interact in different ways in each individual to create huge variations in phenotype

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10
Q

What is the definition of reproductive success?

A

Survival of the form that will leave the most copies of itself in successive generations

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11
Q

What are the ‘genetic forces’ acting on breeds/populations?

A

Selection (natural or artificial)

Loss of genetic diversity (inbreeding or genetic drift)

Immigration

Mutation

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12
Q

When does genetic drift occur?

A

In a SMALL population

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13
Q

What is genetic drift

A

Variation in the relative frequency of different genotypes in a small population, owing to the chance disappearance of particular genes as individuals die or do not reproduce

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14
Q

What can occur secondary to planned selection?

Give an example

A

Unplanned selection

Deafness with the extreme piebald gene in Dalmatians, english setters, collies, Aussies, white boxers and white bull terriers

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15
Q

When is molecular genotyping in dogs useful?

A

Simple inherited disorders - conditions caused by a mutation in just one gene

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16
Q

How are samples obtained for DNA testing in dogs?

A

Blood or mouth swabs

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17
Q

What is the goal of molecular genotyping in dogs?

A

Identify clear, carrier and affected dogs

Effectively reduce or eliminate undesirable disease genes

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18
Q

What animals should you breed together (based on clinical presentation and genotype)?

A

Clinically normal animals

for autosomal recessive, breed clear and carriers etc,

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19
Q

Why shouldn’t you just breed clear to clear?

A

Reduces genetic variation as cuts out half the population

— will result in more diseases

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20
Q

What animals could you breed with an affected dog?

Why?

A

Clear dogs

Will get all carriers as offspring

21
Q

Give examples of some simple genetic conditions.

A

PRA - progressive retinal atrophy
PLL - primary lens luxation
CLAD
copper toxicosis

22
Q

Give examples of diseases caused by complex genetics

A

Hip dysplasia

Elbow dysplasia

Epilepsy

Bloat

23
Q

Which are more common, simple or complex genetic conditions?

A

COMPLEX

24
Q

What can cause differences between genotype and phenotype?

A 
in utero environment 
Neo natal environment 
Feed intake 
Diet 
Exercise
25
Q

What is meant by the term heritability?

A

The proportion of the phenotypic variation made up of variation in the genes

26
Q

What does a higher heritability indicate?

A

We can drive away from the condition by breeding

27
Q

What is the EBV?

A

Estimated breeding value

Tendency of an animal to pass on or develop a disease

Used for complex disease

28
Q

What is the difference between the true and estimated breeding value?

A

True - relevant genotype

Estimated - relevant phenotype

29
Q

What can EBVs be used for?

A

Select towards a positive trait
- milk yield in cows

Select away from a negative trait
- hip dysplasia in dogs

30
Q

When might an individual with bad hips still be used for breeding?

A

If previous generations have good hips, the implication is that good genes are still present

31
Q

What is the difference between binary disease traits and EBVs?

Why might this be beneficial

A

EBVs are continuous

Allow discrimination between ‘healthier’ animals

32
Q

What is the selection intensity?

A

The difference between the mean of selected individuals and the population mean

33
Q

What does an increased selection intensity risk?

A

Decreased genetic diversity

inadvertently be selecting for other diseases

INCREASED RISK OF INBREEDING

34
Q

Why does selection increase risk of inbreeding?

A

Relatives resemble eachother

Selection will result in mating more closely related individuals

35
Q

What is IBD?

A

Identical by descent

Have exact same copy of a gene - same alleles

REDUCED HETEROZYGOCITY

36
Q

What is the COI?

A

Coefficient of Inbreeding

Probability that two copies of a gene at a locus are IBD

0.5 x relationship between parents

37
Q

How can inbreeding lead to specific inherited disease?

A

Reduced number of heterozygotes which ‘hide’ harmful recessive genes

38
Q

What is inbreeding depression?

A

Reduction in beneficial traits as a result of inbreeding

39
Q

What loci does inbreeding depression affect most?

A

Any locus where heterozygous performance is better than homozygote performance

40
Q

What is hybrid vigour?

A

Superior average performance of crossbred progeny compared with the average of their purebreds parent species

41
Q

How long does heterosis / hybrid vigour last for?

A

Deteriorates after first generation

42
Q

What is the effective population size?

A

The number of breeding individuals in a random mating population that would have the same rate of inbreeding as seen in the real population

43
Q

How can the effective population size be calculated?

A

1/ (2x the rate of inbreeding)

44
Q

What is the ideal rate of inbreeding?

A

Less than 0.05%

45
Q

What happens if the effective population size is less than 50?

A

Population fitness steadily declines and becomes UNVIABLE in the long term

46
Q

How can you control the rate of inbreeding?

A

Minimise kinship (coancestry) of matings

Increase number of animals used for breeding

Equalise use of males and females

Monitor genetic contributions

Outcrossing

47
Q

What is outcrossing?

A

Breeding animals in the same breed but with completely separate families

48
Q

What is the ideal effective population size to conserve genetic diversity?

A

> 500

BVetMed3 POS - Integrated Applied Science (2 decks)

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