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B65 Animal Genetic. Lesson Outline Introduction Phenotype Environmental Factors Natural Selection Controlled breeding Two-Breed Cross Three Breed Rotation.

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Presentation on theme: "B65 Animal Genetic. Lesson Outline Introduction Phenotype Environmental Factors Natural Selection Controlled breeding Two-Breed Cross Three Breed Rotation."— Presentation transcript:

1 B65 Animal Genetic

2 Lesson Outline 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

3 Infovets Educational Resources – – Slide 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 Infovets Educational Resources – – Slide 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 Infovets Educational Resources – – Slide 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 Infovets Educational Resources – – Slide 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 Infovets Educational Resources – – Slide 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 Infovets Educational Resources – – Slide 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 Infovets Educational Resources – – Slide 9 Two-Breed Cross  Purebred bulls X purebred cows of another breed  8-10% increase in weaning weight

10 Infovets Educational Resources – – Slide 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 Infovets Educational Resources – – Slide 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 Infovets Educational Resources – – Slide 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 Infovets Educational Resources – – Slide 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 Infovets Educational Resources – – Slide 14 Gene Transfer  Each half is bound together by substances called nucleotides.  There are four main nucleotides:  Adenine  Thiamine  Guanine  Cytosine

15 Infovets Educational Resources – – Slide 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 Infovets Educational Resources – – Slide 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 Infovets Educational Resources – – Slide 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 Infovets Educational Resources – – Slide 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 Infovets Educational Resources – – Slide 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 Infovets Educational Resources – – Slide 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 Infovets Educational Resources – – Slide 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 Infovets Educational Resources – – Slide 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 Infovets Educational Resources – – Slide 23 Punnett Square

24 Infovets Educational Resources – – Slide 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 Infovets Educational Resources – – Slide 25 Monohybrid Cross

26 Infovets Educational Resources – – Slide 26 Monohybrid Cross  What results if two heterozygous animals are mated.

27 Infovets Educational Resources – – Slide 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 Infovets Educational Resources – – Slide 28 Dihybrid Cross Black = 100% Polled = 100% Horned = 0%

29 Infovets Educational Resources – – Slide 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 Infovets Educational Resources – – Slide 30 Dihybrid Cross

31 Infovets Educational Resources – – Slide 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 Infovets Educational Resources – – Slide 32 Dihybrid Cross  If a heterozygous bull (BbPp) is mated to a homozygous cow (BBPP).  What are the outcomes?

33 Infovets Educational Resources – – Slide 33 Dihybrid Cross

34 Infovets Educational Resources – – Slide 34 Dihybrid Cross  If a (BbPp) bull is mated to a (BBPp) cow.  what are the outcomes?

35 Infovets Educational Resources – – Slide 35 Dihybrid Cross

36 Infovets Educational Resources – – Slide 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 Infovets Educational Resources – – Slide 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 Infovets Educational Resources – – Slide 38 Shorthorn: Red X White

39 Infovets Educational Resources – – Slide 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 Infovets Educational Resources – – Slide 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 Infovets Educational Resources – – Slide 41 Genetic Mutations

42 Infovets Educational Resources – – Slide 42 Genetic Mutations  Sometimes genetic mutations can be used to introduce new kinds of species.  Polled Hereford Cattle

43 Infovets Educational Resources – – Slide 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 Infovets Educational Resources – – Slide 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 Infovets Educational Resources – – Slide 45 What Sex Will the Offspring Be?

46 Infovets Educational Resources – – Slide 46 Sex Determination


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