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Genetics By Mr. Gerbitz What is Selection ? Mating animals to produce certain characteristics Low Birth weight Heavier Weaning Weight Color Horned or Polled Temperment What makes an animal they way that they are?

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Mr. Gerbitz

what is selection
What is Selection?
  • Mating animals to produce certain characteristics
  • Low Birth weight
  • Heavier Weaning Weight
  • Color
  • Horned or Polled
  • Temperment
what makes an animal they way that they are
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
what is genetics
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
what are dominant genes
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)
what are recessive genes
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
punnet square
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?
punnet square9
Punnet Square
  • If a homozygous horned cow (PP) is mated to a heterozygous horned bull (Pp), what percent of the calves will be polled?
what are sex linked genes
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
what is incomplete dominance
What is Incomplete Dominance?
  • If both genes express themselves
  • Shorthorn Cattle: Red male mated to a White female = Roan calf
  • RR + WW = RW
punnet square17
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?
punnet square19
Punnet Square
  • If a red bull (RR) is mated to a roan (RW) cow, what color will the calves be?
undesirable characteristics
Undesirable Characteristics
  • Dwarfism
  • Monorchid = only one testicle descends
  • Cryptorchid = no testicles descend
  • Short ears & tails
what is a mutation
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
what is an abnormality
What is an Abnormality?
  • Similar to a Mutation, only it is caused by something in the environment
  • Siamese twins
what is heritability
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
  • 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?
  • 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
mating systems
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
what is hybrid vigor
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
what are exotics
What are Exotics?
  • Animals not common to United States
  • Difficult to define today
  • New breeds are exotics
genetic terms
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)