Animal Breeding and Production with Pedigrees Taylo Cooper · 2018. 12. 20. · Sex-linked Traits...
Transcript of Animal Breeding and Production with Pedigrees Taylo Cooper · 2018. 12. 20. · Sex-linked Traits...
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Animal Breeding and Production with Pedigrees
Taylor Cooper
University of Nebraska–Lincoln
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DNA, Chromosomes, & Genes
✓ Number & size of chromosomes differ by species➢Humans: 23 pairs of chromosomes
• 22 pairs of autosomes
• 1 pair of sex chromosomes
➢ Pigs – 19 pairs
➢Cattle – 30 pairs
➢Dogs – 39 pairs.
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Recessive vs. Dominant Traits
✓ Dominant Trait = trait that is expressed in an offspring if a parent give that traitWill be expressed both if both parents pass it down
or if one does➢Humans-black hair is dominant
✓ Recessive Trait = trait that is carried by a person without appearing in person Requires both parents to pass the recessive gene
down for it to be expressed in offspring Humans-red hair is recessive
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Genotype vs. Phenotype
✓ Genotype = genetic makeup of a trait➢“BB” vs “Bb” vs “bb”
✓ Phenotype = expressed characteristics➢ Influenced by BOTH Genetics & Environment
➢Color of Hair/Fur
➢Color Blindness
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Punnett Square:
B
b
B b
BB Bb
bB bb
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Pedigrees
✓ Are the records that show patterns of inheritance
✓ Useful in determining if a trait is dominant or recessive in a family line➢ Can be used to determine if a trait is sex-linked or
autosomal
✓ Allows genetic disorders to be tracked through multiple generations
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What is on a Pedigree?
✓ Name
✓ Registration number
✓ Type rating
✓ Production record
✓ Show-ring winnings
✓ Study carefully they can sometimes be misleading
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Pedigree Symbols
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What are the genotypes of each person in this pedigree?
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Autosomal Traits
✓ Trait not dependent on sex-will be expressed on a autosome chromosome
✓ Autosomal dominant inheritance = only one copy of allele is necessary for an individual to express traitMyotonic muscular dystrophy or Huntington disease
Autosomal recessive inheritance = two copies of a disease allele are required for an individual to express trait Sickle cell anemia
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Sex-linked Traits Trait linked to a sex chromosome-normally linked to
X chromosome
X-linked dominant inheritance = only one copy of an allele on X chromosome is required for an individual to be susceptible Fragile X syndrome
X-linked recessive inheritance = two copies of a disease allele on the X chromosome are required for an individual (in females) Hemophilia A
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Calculation of Breed Genetics
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Uses of Pedigrees
✓ Different based on species:➢ Humans = tracking genetic disease
➢ Dairy cattle = ancestry milk production
➢ Horses = racing results, showing results
➢ Meat Production Animals (cattle, hogs, poultry) = purebreds or evaluating breeding probability
➢ Dogs = purebreds
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Evaluating Animals✓ Can’t just use pedigrees when evaluating animals
for breeding and production purproses
✓ Need to look at production records➢ Milk = Dairy cattle, goats
➢ Eggs = Poultry
➢ Wool = Sheep
✓ Health Records
✓ Expected Progeny Difference (EPDs)➢ Beef Cattle, Hogs, Sheep, etc.
✓ Live Evaluations➢ Structure, Muscling, Finish
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Key Points: Pedigrees
✓ Dominant vs. Recessive Traits
✓ Genotype vs. Phenotypes
✓ Pedigrees a record of the ancestry of individual➢ Used for genetic diseases, determining traits, purebred
records
✓ Autosomal vs. X-linked traits and inheritance
✓ Pedigrees aren’t the only thing used to select production and breeding livestock
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