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Inbreeding depression - PowerPoint PPT Presentation


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Lecture 24. Mating Systems. Inbreeding. Inbreeding. -- Increases homozygosity (uniformity => like gametes , like individuals). Inbreeding. -- Disadvantages of Inbreeding --. Inbreeding. -- Disadvantages of Inbreeding -- 1) inbreeding exposes deleterious genes. Inbreeding.

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slide1

Lecture 24

Mating Systems

slide3

Inbreeding

-- Increases homozygosity (uniformity => like gametes , like individuals)

slide4

Inbreeding

-- Disadvantages of Inbreeding --

slide5

Inbreeding

-- Disadvantages of Inbreeding --

1) inbreeding exposes deleterious genes

slide6

Inbreeding

-- Disadvantages of Inbreeding --

1) inbreeding exposes deleterious genes

2) inbreeding depression --reduced performance due to increased homozygosity, exposing genes with negative effects

slide7

Inbreeding

-- Disadvantages of Inbreeding --

1) inbreeding exposes deleterious genes

2) inbreeding depression --reduced performance due to increased homozygosity, exposing genes with negative effects

--high risk (complete lines can be lost)

inbreeding depression
Inbreeding depression

Reduction in fitness in inbred individuals

  • Juvenile survival
  • Adult survival
  • Mate acquisition
  • Social dominance
  • Fertility and Fecundity
  • Growth
inbreeding depression11
Inbreeding depression

Reduction in fitness in inbred individuals

  • Proper development
  • Disease resistance
  • Resistance to environmental stresses
  • Metabolic efficiency
  • Sensory acuity
non inbred vs inbred crested wood partridges at the mn zoo
Non-Inbred vs. Inbred Crested Wood Partridges at the MN Zoo
  • 8% reduction in egg volume
  • 10% reduction in egg weight
  • 20% reduction in hatch rate
  • 51% reduction in 30 day survival
  • Non-inbred birds have 41% fewer medical notes than their inbred counterparts!
slide16

Line breeding

-- mating system design to maintain a high degree of relatedness of descendants to a particular ancestor (mild form of inbreeding) --

slide17

Line breeding

Generation A “super star”

1 B 1/2

slide18

Line breeding

Generation A “super star”

1 B 1/2

2 C 1/4

slide19

Line breeding

Generation A “super star”

1 B 1/2

2 C 1/4

3 D 1/8

slide20

Line breeding

Generation A “super star”

1 B 1/2

2 C 1/4

3 D 1/8

--Very quickly we lose the gene combinations that defined the superstar.--

slide21

Line breeding

A

1 B C D 1/2

aF

slide22

Line breeding

A

1 B C D 1/2

2 E 1/2 1/8

aF

slide23

Line breeding

A

1 B C D 1/2

2 E 1/2 1/8

3 F 1/2 1/4

aF

slide24

Line breeding

A

1 B C D 1/2

2 E 1/2 1/8

3 F 1/2 1/4

aF

Note: The relationship is high but F is reasonably low.

example of crosses
Example of Crosses

PB1

PB2

F1

×

×

×

Backcross

Backcross

F2

slide27

Cross Breeding

-- crossing of animals from different breeds --

slide28

Cross Breeding

-- crossing of animals from different breeds --

--Breed --

subpopulation of a species inter se mated with the objective of maintaining particular characteristics that define the group.

slide29

Differentiation in Breeds

1) Different objectives using artificial selection

slide30

Differentiation in Breeds

1) Different objectives using artificial selection

Example: Holstein -- milk

Hereford -- beef

Simmental -- dual purpose

slide31

Differentiation in Breeds

2) Originate in different environments and are influenced differently by natural selection

slide32

Differentiation in Breeds

2) Originate in different environments and are influenced differently by natural selection

Example: Brahman versus Hereford

slide33

Differentiation in Breeds

2) Originate in different environments and are influenced differently by natural selection

Example: Brahman versus Hereford

heat dissipation, Brahman cattle:

have less hair, sweat versus pant, have smaller metabolic organs, lower birth weights and thicker hides

slide34

Differentiation in Breeds

Over time breeds come to represent different reservoirs of genes:

slide35

Differentiation in Breeds

Over time breeds come to represent different reservoirs of genes:

1) different alleles

slide36

Differentiation in Breeds

Over time breeds come to represent different reservoirs of genes:

1) different alleles

2) different frequencies

slide37

Differentiation in Breeds

Growth Hormone Alleles

Angus Brahman allele

1.0 .30 A

0 .17 B

0 .38 C

0 .20 D

slide39

Reasons for Crossbreeding

1) Complementarity -- combine breeds to take advantage of the best characteristics for both breeds

slide40

Reasons for Crossbreeding

1) Complementarity -- combine breeds to take advantage of the best characteristics for both breeds

2) Method of migration of new genotypes

slide41

Reasons for Crossbreeding

1) Complementarity -- combine breeds to take advantage of the best characteristics for both breeds

2) Method of migration of new genotypes

3) Creating synthetic breeds -- combining breeds then inter se mating to form a new breed

slide42

Reasons for Crossbreeding

1) Complementarity -- combine breeds to take advantage of the best characteristics for both breeds

2) Method of migration of new genotypes

3) Creating synthetic breeds -- combining breeds then inter se mating to form a new breed

4) Rapid change in performance

slide43

Reasons for Crossbreeding

Example: 1969 -- less than 15 Simmental bulls imported in the US

slide44

Migrating New Genotypes

A × B Generation

slide45

Migrating New Genotypes

A × B Generation

A × 1/2A + 1/2B 1

slide46

Migrating New Genotypes

A × B Generation

A × 1/2A + 1/2B 1

A × 3/4A + 1/4B 2

slide47

Migrating New Genotypes

A × B Generation

A × 1/2A + 1/2B 1

A × 3/4A + 1/4B 2

A × 7/8A + 1/8B 3

slide48

Migrating New Genotypes

A × B Generation

A × 1/2A + 1/2B 1

A × 3/4A + 1/4B 2

A × 7/8A + 1/8B 3

[1 - (1/2)t]A + [(1/2)t]B t

slide49

Creating Synthetics

Example: Brangus (3/8 Brahman and 5/8 Angus)

slide50

Creating Synthetics

Example: Brangus (3/8 Brahman and 5/8 Angus)

Angus Brahman

1/2A 1/2B

slide51

Creating Synthetics

Example: Brangus (3/8 Brahman and 5/8 Angus)

Angus Brahman

1/2A 1/2B Brahman 1/4A 3/4B

slide52

Creating Synthetics

Example: Brangus (3/8 Brahman and 5/8 Angus)

Angus Brahman

1/2A 1/2B Brahman Angus 1/4A 3/4B

5/8A 3/8B  BRANGUS

slide53

Computing Fractions

GH x Lab

(1/2) GH (1/2) Lab

(1) GH x (1/2) GH (1/2) Lab

(3/4) GH (1/4) Lab

(3/4) GH (1/4) Lab x (1/2) GH (1/2) Lab

slide54

Computing Fractions

(3/4) GH (1/4) Lab x (1/2) GH (1/2) Lab

What is the expected fraction of GH and Lab genes in a progeny resulting from this mating?

slide55

Computing Fractions

(3/4) GH (1/4) Lab x (1/2) GH (1/2) Lab

GH = (¾) x (1/2) + (1/2) x (1/2) = 5/8

Lab = (1/4) x (1/2) + (1/2) x (1/2) = 3/8

slide56

Rapid Change

Example: Targhee and Finn

slide57

Reasons for Crossbreeding

Targhee -- 1.1 lambs/ ewe

1.5 lambs/ ewe

6 generations

slide58

Reasons for Crossbreeding

Targhee -- 1.1 lambs/ ewe

1.5 lambs/ ewe

Finn -- 2.6 lambs/ ewe

2.1 lambs/ ewe

6 generations

1 generation (1/2F 1/2T)

slide59

Reasons for Crossbreeding

Targhee -- 1.1 lambs/ ewe

1.5 lambs/ ewe

Finn --2.6 lambs/ ewe

2.1 lambs/ ewe

6 generations

selection

1 generation (1/2F 1/2T)

cross breeding

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