13: Genetic Resemblance Flashcards

1
Q

What % of DNA does an individual share with their parents? Great grandparents?

A

Parents = 50%
Great grandparents = 12.5%

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2
Q

Why do we expect relatives to perform alike?

A

Similar genotypes, developed in similar environment

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3
Q

Definition of the ‘relationship’ between relatives

A

The proportion of genes that two individuals have in common because they are members of the same family

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4
Q

What is a common ancestor

A

An ancestor common to more than one individual or an ancestor common to the parents of an inbred individual

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5
Q

Inter vs intraclass

A

Interclass = relationship between parents and their offspring (two diff generations)
Intraclass = relationship among siblings (same class)

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6
Q

What are ancestor relatives? Collateral relatives?

A

Ancestor relatives are interclass relatives (parent and offspring)
Collateral relatives are intraclass relatives (full or half siblings)

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7
Q

Why is genetic resemblance between relatives important in animal breeding?

A
  • estimate variance, covariances, and genetic parameters
  • used for genetic selection and breeding methods
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8
Q

The amount of phenotypic resemblance among relatives for a trait provides an indication of…

A

the amount of genetic variation for that trait

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9
Q

If the trait has significant genetic basis, the closer the relatives…

A

the more similar their appearance

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10
Q

Two animals are genetically related when

A

they have at least one common ancestor

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11
Q

What is identical by descent?

A

Both copies of the same gene can be traced back to a single copy in a recent common ancestor
Individual is homozygous at a locus because some of their ancestors were related

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12
Q

What is identical by state? Aka

A

When alleles are equal (homozygous) but they derive from different animals in the reference population
aka alike in state

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13
Q

Second definition of ‘relationship’ between relatives

A

The probability that a randomly taken allele from individual X is identical by descent to a randomly taken allele from individual Y

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14
Q

What is inbreeding

A

The mating of relatives (animals more closely related than average of pop)

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15
Q

Inbreeding causes an increase in the… and a decrease in the…

A

proportion of loci at which an individual is homozygous

proportion of loci at which an individual is heterozygous

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16
Q

Outcomes of inbreeding

A

Increased homozygosity (alleles IBD)
Increased expression of deleterious recessive alleles
Increased prepotency

17
Q

What is prepotency

A

The ability of an individual to produce progeny whose performance is especially like its own and/or is especially uniform

18
Q

How does prepotency work

A

Inbred animals produce fewer unique gametes and therefore fewer unique zygotes leading to low variability in their progeny

19
Q

Examples of the expression of deleterious recessive alleles

A

Spider leg condition in sheep, dwarfism in cattle

20
Q

Does inbreeding create deleterious recessive alleles?

A

No, they must already be present in a pop
They just increase expression

21
Q

Expression of deleterious recessive alleles leads to…

A

reduced fitness (survivability, fertility)

22
Q

What is inbreeding depression

A

Decrease in the performance of inbred animals due to the expression of unfavorable alleles influencing polygenic traits

23
Q

What is inbreeding depression with regards to quantitative traits

A

Manifestation of unfavorable gene combination value resulting from increased homozygosity (reduced hybrid vigor)

24
Q

Inbreeding depression and hybrid vigor are functions of…

A

GCV (NOT BV)

25
The more homozygous gene combinations an individual has, the less its... and ultimately its...
less its gene combination value, its genotypic value and ultimately its performance
26
Inbreeding depression and hybrid vigor are also affected by the...
degree of dominance exhibited at each locus
27
Why do we use inbreeding strategy?
- identify deleterious recessive alleles in a pop - increase uniformity in a breed (e.g. coat colour) - increase hybrid vigor by crossing inbred lines or purebred animals (outbreeding)
28
What is outbreeding? What are the outcomes?
Mating of individuals more distantly related than average for population Aka crossbreeding Increases heterozygosity Masks expression of deleterious recessive alleles Results in increased GCV (increased hybrid vigor)
29
Why use outbreeding?
Avoid appearance of inbreeding, cover existence of deleterious recessive alleles Add hybrid vigor (favourable GCV) Take advantage of breeding complimentary