Genetics

1. Genetics

2. Genetics Terms • Heterozygous = two different types of genes (Bb) • Homozygous = two similar genes (BB) • Dominant Gene = trait overpowers others • Recessive Gene = must be accompanied with another recessive gene to express trait • Incomplete Dominance = both traits express themselves

3. Genetic Terms • Genotype - genetic makeup (Bb) • Phenotype - physical appearance (Black) • Heterosis - Genes are different, Dominant & Recessive (Bb)

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

5. What makes an animal the way it is? • Animals are result of Feed, Health, and Inheritance(genetic material) • Feed is fastest to correct • Genetics last longest

6. What are 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

7. What are Dominant Genes? • Dominant Genes are traits that overpower other types of genes • Angus Cattle: black(B) color dominant, red (b) color recessive (Bb) • Hereford: white (W) face cattle dominant over colored (w) recessive (Ww) • Hampshire Hog: white (W) belt dominant, color (w) recessive (Ww) • Polled (P) cattle are dominant over horned (p) recessive (Pp) • Black (B) horses dominate, brown (b) recessive (Bb)

8. 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

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

10. p p P Pp Pp P Pp Pp Punnet Square

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

12. Punnet Square P p P PP Pp P PP Pp

13. 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

14. Punnet Square:What sex will the offspring be? X Y X XX XY X XX XY

15. If dad is bald, will you be bald? X Y B X X X X Y B X X XY X B

16. Baldness is carried by the mother X Y X X X X Y B B B X X X Y X

17. What if mom is bald? X Y X X X X Y B B B X X X X Y B B B

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

19. 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?

20. Shorthorn: Red X White R R RW RW W W RW RW

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

22. Shorthorn: Red X Roan R R R RR RR W RW RW

23. What if Both Parents are Roan? R W R RR RW W RW WW

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

25. 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

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

27. 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

28. 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?

29. 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

30. 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

31. Crossbreeding • mating of animals of different breeds • can increase productivity • produce animals with combination of traits • foundation stock for new breeds • introduce new genes quicker than in purebreds

32. What is Hybrid Vigor? • Offspring will out-perform either of the parents, also know as heterosis. • 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

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