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Genetics

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  1. Genetics By Mr. Gerbitz

  2. What is Selection? • Mating animals to produce certain characteristics • Low Birth weight • Heavier Weaning Weight • Color • Horned or Polled • Temperment

  3. 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

  4. 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

  5. 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)

  6. 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

  7. 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?

  8. Punnet Square

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

  10. Punnet Square

  11. 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

  12. Punnet Square: What sex will the offspring be?

  13. If Dad is bald, will you be bald?

  14. Baldness is carried by the mother

  15. What is Mom is bald?

  16. What is Incomplete Dominance? • If both genes express themselves • Shorthorn Cattle: Red male mated to a White female = Roan calf • RR + WW = RW

  17. 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?

  18. Shorthorn: Red X White

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

  20. Shorthorn: Red X Roan

  21. What if Both Parents are Roan?

  22. Undesirable Characteristics • Dwarfism • Monorchid = only one testicle descends • Cryptorchid = no testicles descend • Short ears & tails

  23. 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

  24. What is an Abnormality? • Similar to a Mutation, only it is caused by something in the environment • Siamese twins

  25. 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

  26. 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?

  27. 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

  28. 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

  29. 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

  30. What are Exotics? • Animals not common to United States • Difficult to define today • New breeds are exotics

  31. 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)