Genetics

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Genetics

• Original Power Point Created by Casey Osksa
• Modified by Georgia Agricultural Education
  Curriculum Office
• June 2002

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What is Selection?

• Mating animals to produce certain characteristics
• Low Birthweight
• Heavier Weaning Weight
• Color
• Horned or Polled
• Temperment

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What makes an animal they way that they are?

• Animals are the result of Feed, Health, and
  Inheritance (genetic material)
• Feed is fastest to correct
• Genetics last longest

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What is Genetics?

• All body cells contain Blueprints with
  instructions as to how an animal will look or act
  etc.
• One Gene comes from each parent (pairs)
• Genes are divided into sections (Chromosomes)
  that carry genes
• Sex chromosomes male XY, female XX

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What are Dominant Genes?

• Dominant Genes one gene overshadows the other
• Angus Cattle black is dominant, red is not (Bb)
• Hereford white face is dominant (Ww)
• Hampshire Hog white belt is dominant
• Horns are dominant (Pp)

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What are Recessive Genes?

• The gene that is overshadowed by a dominant gene
• Recessive genes can only express themselves if
  both genes are recessive
• Polled vs Horned (Pp) (pp)
• Black wool vs white (Ww) (ww)
• Dwarfism vs normal size (dd)
• Albino

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Punnet Square

• P horned
• p polled
• If a homozygous horned cow (PP) is mated to a
  homozygous polled bull (pp), what percent of the
  calves will be horned, polled?

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Punnet Square
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Punnet Square

• If a homozygous horned cow (PP) is mated to a
  heterozygous horned bull (Pp), what percent of
  the calves will be polled?

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Punnet Square
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What are Sex Linked Genes?

• Some recessive genes are attached to the X and Y
  chromosomes
• Humans Colorblindness and Baldness are on the X
  chromosomes
• In Men, traits expressed anytime present
• In Women, must have two recessives to show trait
• Children get baldness from mothers

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Punnet Square What sex will the offspring be?
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If Dad is bald, will you be bald?
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Baldness is carried by the mother
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What if Mom is bald?
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What is Incomplete Dominance?

• If both genes express themselves
• Shorthorn Cattle Red male mated to a White
  female Roan calf
• RR WW RW

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Punnet Square

• Shorthorn Cattle
• R Red
• W white
• RW roan
• If a red bull (RR) is mated to a white cow (WW),
  what color will the calves be?

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Shorthorn Red X White
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Punnet Square

• If a red bull (RR) is mated to a roan (RW) cow,
  what color will the calves be?

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Shorthorn Red X Roan
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What if Both Parents are Roan?
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Undesirable Characteristics

• Dwarfism
• Monorchid only one testicle descends
• Cryptorchid no testicles descend
• Short ears tails

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What is a Mutation?

• Dramatically different from what is expected
  genetically
• Horned calf from polled parents
• Loss of some or extra body parts
• Lethal Mutation causes death at birth
• Sublethal Mutation limits animals ability to
  grow to maturity
• Beneficial Mutation loss of tail in lambs

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What is an Abnormality?

• Similar to a Mutation, only it is caused by
  something in the environment
• Siamese twins

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What is Heritability?

• Chance that traits will be inherited
• Low multiple births, fat covering
• Medium birth wt, wean wt, milk, wool grade,
  carcass wt, rate of gain
• High Loin eye area, fleece length quality

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Heritability

• Currently have ewes that wean 70 lb lambs
• Want to raise weaning wt to 110 lbs
• Select a ram with a wean wt of 110 lbs
• Heritability of weaning wt is 30
• What can you expect new lamb crop to weigh at
  weaning?

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Heritability

• What is the difference in current weaning wt and
  that of the new ram?
• 110 - 70 40 lbs
• Heritability x difference
• 30 x 40 12 lbs
• Can expect a gain in weaning wt of 12 lbs
• 70 lbs 12 lbs 82 lbs

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Mating Systems

• Random Mating all males have an equal
  opportunity to mate with all females
• Outcrossing mating purebreds with unrelated
  purebreds
• Inbreeding mating related animals
• Linebreeding parents mated to offspring
• Crossbreeding mating animals of same species but
  different breeds

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What is Hybrid Vigor?

• Offspring will outperform either of the parents
• Corn Breed A yields 100 bu/acre
• Corn Breed B yields 100 bu/acre
• Crossbreed A B yields corn that yields 200
  bu/acre
• Vigor only expressed in crossbreeding
• Donkey mated to a horse Mule
• mule is sterile

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What are Exotics?

• Animals not common to United States
• Difficult to define today
• New breeds are exotics

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Genetic Terms

• Genotype genetic makeup (Bb)
• Phenotype physical appearance (Black)
• Heterosis Genes are different, Dominant
  Recessive (Bb)
• Homozygous both genes are the same (BB or bb)