B65 Animal Genetic

1. B65 Animal Genetic

2. Introduction Phenotype Environmental Factors Natural Selection Controlled breeding Two-Breed Cross Three Breed Rotation Cross Gene Transfer Genetic Engineering Differentiation Alleles Gene Dominance Punnett Square Mendilin Genetics Codominate Genes Additive Expression of Genes Lesson Outline

3. Introduction • No two animals are exactly alike. Even with twins one may be taller, one may be heavier, or grow faster. • The two main factors that contribute to these differences in animals are: • The environment. • The genetic make up of the animal.

4. Phenotype • The phenotype is the physical appearance of the animal. • The genotype is the genetic make up of the animal • Both the environment and the genetic make up effect the physical appearance of the animal.

5. Environmental Factors • The quantity and quality of the feed • Climate conditions • Exposure to parasites and diseases • The type of terrain (steep mountains, desserts, irrigated pasture) • The producer has a lot of control over the animal’s environment. • A producer can also influence, to a lesser degree, the genetic make up of an animal.

6. Natural Selection • In nature, genetics are passed on through the process of natural selection. The strongest, healthiest, most powerful animal generally spreads its genetics. Animals that are weak may have a poor immune system and are diseased, or may have conformation problems. Generally these animals do not survive long enough to pass on their genetics.

7. Controlled Breeding • A producer crosses two parents based on a desired outcome. • A tough, dominant, alpha male may not be a desirable trait for domestic animals. • Agriculture producers select for traits that have economic importance, such as low birth weight, growth rate, feed efficiency, mothering ability, carcass traits. • The economically important traits are influenced by both the environment and the genetic make up of the animal.

8. Controlled Breeding Programs • Outcrossing: Breeding purebred animals with unrelated purebred animals. • Cross Breeding: Breeding animals of the same species but of a different breed. • Hybrid Vigor or Heterosis: • A biological phenomenon which causes crossbreeds to out produce the average of their parents • Will achieve 15 to 25% immediate increase in yield • The more dissimilar the breeds, the greater the heterosis: (British breed crossed with Zebu breed)

9. Two-Breed Cross • Purebred bulls X purebred cows of another breed • 8-10% increase in weaning weight

10. Two-Breed Backcross or Crisscross • Breed A X Breed B = Crossbred calves • Crossbred X Breed A or B • Charolais Bull X Hereford Cow = Cross • Cross X Charolais • Yields 67% of maximum heterosis

11. Three Breed Rotation Cross • 3 Breeds (Angus, Simmental, Charolais) • Crossbred females bred to purebred bull of breed A • Resulting cross mated to purebred bull of breed B • Resulting cross mated to purebred bull of breed C • Repeat rotation • 87% of maximum heterosis

12. Gene Transfer • All selection is based on the concept that desired characteristics are passed on from the parents to the offspring. • Humans have 46 chromosomes. Each parent contributes 23. • A chromosome is a long protein strand on molecules called DNA. • DNA is made up of segments called genes.

13. Gene Transfer • Each gene is responsible for a particular trait. • Genes form a code or a blueprint for how the animal is to be formed. • One chromosome (strand of DNA) will attach to another forming a spiral shape called a double helix.

14. Gene Transfer • Each half is bound together by substances called nucleotides. • There are four main nucleotides: • Adenine • Thiamine • Guanine • Cytosine

15. Gene Transfer • Nucleotides are shaped so that each substance can pair with one particular nucleotide. • Adenine can only pair with thiamine. • Cytosine can only pair with guanine. • When cells undergo mitosis and divide, each half replicates itself so two strands exactly alike are formed. (DNA replication).

16. Gene Transfer • The genetic sequence on the DNA is used as a pattern for how the animal is to be constructed. RNA (Ribonucleic acid) reads the pattern and transfers the information to the rest of the cell.

17. Genetic Engineering • Genetic engineering is a technology that allows specific genetic information or traits to be built into or engineered into the genes of a species. • In genetic engineering, segments of DNA are cut and spliced into existing DNA, placing new genetic information into the existing DNA.

18. Differentiation • As the embryo begins to grow and develop, cells differentiate. Some cells develop into muscle and bone, some into skin and some into internal organs. • The process of how cells differentiate is not fully understood.

19. Differentiation • Sex cells called gametes undergo meiosis and only carry one strand of DNA. • At conception, chromosome halves from each parent combine to form a paired chromosome. • There is almost an infinite number of ways that the genes can be arranged on a strand of DNA. This arrangement determines the make up of the new animal.

20. Alleles • Each male gene that controls a specific trait combines with the female gene for the same trait. • A pair of genes that control a specific trait are called alleles. • If both genes that control a specific trait are alike, they are said to be homozygous. • For example, if the male gene for hair color is black and the female gene that controls hair color is also black.

21. Gene Dominance • If they are different (black & red), they are said to be heterozygous. • In this case one gene will be dominate and determine coat color. • Dominant gene = trait overpowers others • Recessive gene = must be accompanied with another recessive gene to express trait

22. Gene Dominance • P = polled • p = horned • Genotype is the genetic make up of the animal. • Phenotype is the physical appearance of the animal. • If a homozygous horned cow (pp) is mated to a homozygous polled bull (PP), what will the genotypic and phenotypic ratio of the calves be?

23. Punnett Square

24. Monohybrid Cross • A monohybrid cross is an estimation of a predicted outcome for a single trait. • If a homozygous horned cow (pp) is bred with a heterozygous polled bull (Pp), what percent of the calves will be polled?

25. Monohybrid Cross

26. Monohybrid Cross • What results if two heterozygous animals are mated.

27. Dihybrid Cross • A dihybrid cross is a estimation of a predicted outcome for two traits. • What results if an Angus bull that is homozygous black and polled (BBPP) is bred with a red shorthorn cow which is homozygous red and horned (bbpp). • The bull BBPP can be simplified to BP (black & polled is the only possible contribution for the bull). • The cow bbpp can be simplified to bp (red & horned is the only possible contribution for the cow).

28. Dihybrid Cross Black = 100% Polled = 100% Horned = 0%

29. Dihybrid Cross • Now if two of the offspring which are heterozygous for black/red and polled/horned (BbPp) are mated. • How do you do a Punnett square for two heterozyous animals? • Use all possible gene combinations. • Both the bull and cow are BbPp. • What are the possible contributions? • BP, Bp, bP, bp for both animals. (4 x 4 grid)

30. Dihybrid Cross

31. Dihybrid Cross • Black Polled = 9 out of 16 or 56.25% • Black Horned = 3 out of 16 or 18.75% • Red Polled = 3 out of 16 or 18.75% • Red Horned = 1 out of 16 or 6.25%

32. Dihybrid Cross • If a heterozygous bull (BbPp) is mated to a homozygous cow (BBPP). • What are the outcomes?

33. Dihybrid Cross

34. Dihybrid Cross • If a (BbPp) bull is mated to a (BBPp) cow. • what are the outcomes?

35. Dihybrid Cross

36. Mendilin Genetics • Paint color is a desirable characteristic of paint horses and is dominate to solid color. • If a homozygous dominate stallion is bred with a solid colored mare, how likely is it that a paint foal will result? • What if the stallion is heterozygous for paint color?

37. Codominate Genes • Some alleles may have two dominate genes. • Shorthorn cattle are red, white or roan. • Red shorthorns carry the gene for red coat color RR. • White shorthorns carry the gene for white coat color WW. • Cattle that are roan or spotted carry a gene for red and a gene for white RW. • Both are dominant, creating a spotted or roan colored animal.

38. Shorthorn: Red X White

39. The Additive Expression of Genes • Instead of a single pair, a number of genes may be added together to produce a single trait. • Examples: • Milk production is controlled by several genes. • Size and body capacity of the female • Hormone production • Mammary size and function • Rate of gain • Reproduction

40. Genetic Mutations • Occasionally a defect will happen and genetic traits are not passed on as intended. • Example: two headed calves • An abnormality is similar to a mutation, only it is caused by something in the environment

41. Genetic Mutations

42. Genetic Mutations • Sometimes genetic mutations can be used to introduce new kinds of species. • Polled Hereford Cattle

43. Determining an Animal’s Sex • Whether a mammal is a male or a female is determined upon conception. • Gamete (sex cell) contains one half of the sex chromosome from the parent. • The female chromosome is referred to as XX. • When the chromosome divides and half goes to the offspring each half is the same.

44. Determining an Animals Sex • The male chromosome is referred to as XY. And when divided, a gamete will be either X or Y. • When the male and female gamete combine they will either be XX female or XY male. • What is the probability of a male being conceived over a female child?

45. What Sex Will the Offspring Be?

46. Sex Determination