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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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Extension is a Division of the Institute of Agriculture and Natural Resources at the University of Nebraska–Lincoln cooperating with the Counties and the United States Department of Agriculture.

The Youth Development program abides with the nondiscrimination policies of the University of Nebraska–Lincoln and the United States Department of Agriculture.