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Illustration of DNA Double Helix from Wikipedia. ANIMAL GENETICS Agriscience 332 Animal Science #8406 TEKS: (c)(4)(B)

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Presentation on theme: "Illustration of DNA Double Helix from Wikipedia. ANIMAL GENETICS Agriscience 332 Animal Science #8406 TEKS: (c)(4)(B)"— Presentation transcript:

1 Illustration of DNA Double Helix from Wikipedia. ANIMAL GENETICS Agriscience 332 Animal Science #8406 TEKS: (c)(4)(B)

2 Illustration of DNA Double Helix from Wikipedia. Introduction Genetics is the science of heredity and variation. It is the scientific discipline that deals with the differences and similarities among related individuals.

3 Illustration of DNA Double Helix from Wikipedia. All animals have a predetermined genotype that they inherit from their parents. However, an animal’s genotype can be manipulated by breeding and more advanced scientific techniques (genetic engineering and cloning).

4 Illustration of DNA Double Helix from Wikipedia. For many years, managers of agricultural systems have manipulated the genetic makeup of animals to improve productivity and increase efficiency. Successful manipulation of the genetic composition of animals requires an understanding of some fundamental principles of genetics.

5 Illustration of DNA Double Helix from Wikipedia. Mendelian Genetics Gregor Mendel is recognized as the father of genetics. Mendel, who was not scientifically trained, developed his theories in the 1850’s and 1860’s, without any knowledge of cell biology or the science of inheritance. Photo courtesy of Wikipedia.

6 Illustration of DNA Double Helix from Wikipedia. In later years, genes, chromosomes, and DNA were discovered and people began to understand how and why Mendel’s theories worked.

7 Illustration of DNA Double Helix from Wikipedia. Mendel proposed three principles to describe the transfer of genetic material from one generation to the next. The Principle of Dominance The Principle of Segregation The Principle of Independent Assortment

8 Illustration of DNA Double Helix from Wikipedia. The Principle of Dominance – in a heterozygous organism, one allele may conceal the presence of another allele.

9 Illustration of DNA Double Helix from Wikipedia. The Principle of Segregation – in a heterozygote, two different alleles segregate from each other during the formation of gametes.

10 Illustration of DNA Double Helix from Wikipedia. The Principle of Independent Assortment – the alleles of different genes segregate, or assort, independently of each other.

11 Illustration of DNA Double Helix from Wikipedia. Later studies have shown that there are some important exceptions to Mendel’s Principle of Independent Assortment, but otherwise, these principles are recognized as the basis of inheritance.

12 Illustration of DNA Double Helix from Wikipedia. Mendel’s experiments dealt with the relationship between an organism’s genotype and its phenotype. Genotype – the genetic composition of an organism. Phenotype – the observable or measurable characteristics (called traits) of that organism.

13 Illustration of DNA Double Helix from Wikipedia. Two organisms may appear to be similar, but they can have different genotypes. Similarly, two animals may have the same genotypes, but will appear to be different from each other, if they have been exposed to different environmental conditions throughout their lives.

14 Illustration of DNA Double Helix from Wikipedia. The relationship between phenotype and genotype is expressed as the following equation: P = G + E P = phenotype, G = genotype, and E = environment.

15 Illustration of DNA Double Helix from Wikipedia. If two individuals with identical genotypes are exposed to the same environmental conditions, such as nutrition, climate, and stress levels, their phenotypes (measurable and observable characteristics) should be the same.

16 Illustration of DNA Double Helix from Wikipedia. To understand Mendel’s principles and the relationships between phenotype and genotype, it is necessary to understand what makes up the genetic material of animals and how this is transferred from one generation to the next.

17 Illustration of DNA Double Helix from Wikipedia. Genetic Material The body is made up of millions of cells which have a very complicated structure. These cells are made up of many parts that have specialized roles.

18 Illustration of DNA Double Helix from Wikipedia. 1. Nucleolus5. Rough Endoplasmic Reticulum9. Mitochondria 2. Nucleus6. Golgi Aparatus10. Vacuole 3. Ribosome7. Cytoskeleton11. Cytoplasm 4. Vesicle8. Smooth Endoplasmic Reticulum12. Lysosome 13. Centrioles Courtesy of Wikipedia

19 Illustration of DNA Double Helix from Wikipedia. The nucleus contains chromosomes that are visible under the microscope as dark- staining, rod-like or rounded bodies.

20 Illustration of DNA Double Helix from Wikipedia. Chromosomes occur in pairs in the body cells. The number of chromosomes in each cell is constant for individual species, but it differs among species.

21 Illustration of DNA Double Helix from Wikipedia. Chromosomes are made up of tightly-coiled strands of DNA. DNA is a complex molecule composed of deoxyribose, phosphoric acid, and four bases. Individual genes are located in a fixed position (known as the loci) on the strands of DNA.

22 Illustration of DNA Double Helix from Wikipedia. A Chromosome A chromosome is made up of two chromatids and a centromere. The chromatids are formed from tightly coiled strands of DNA. If these strands of DNA are stretched out, individual genes can be identified.

23 Illustration of DNA Double Helix from Wikipedia. A gene is made up of a specific functional sequence of nucleotides, which code for specific proteins. A specific protein is produced when the appropriate apparatus of the cell (the ribosome) reads the code. Image courtesy of Wikipedia.

24 Illustration of DNA Double Helix from Wikipedia. The collection of genes that an organism has is called its genome. Photo by Peggy Greb courtesy of USDA Agricultural Research Service.

25 Illustration of DNA Double Helix from Wikipedia. In somatic cells (body cells), chromosomes occur in pairs, known as homologous chromosomes. As a result, genes also occur in pairs. Somatic cells are referred to as diploid, or 2n.

26 Illustration of DNA Double Helix from Wikipedia. Gametes (reproductive cells) do not have paired chromosomes and are referred to as haploid, or n.

27 Illustration of DNA Double Helix from Wikipedia. Cell Division Cells must divide and increase in number so that animals can grow. A new cell is formed when one cell divides. Mitosis and meiosis are the two processes by which cells divide.

28 Illustration of DNA Double Helix from Wikipedia. Mitosis is the type of cell division in which the genetic material in the parent cell is duplicated and then divides into two separate cells with identical genetic material. Both new cells are diploid (2n) with a complete set of chromosomes identical to those in the parent cell.

29 Illustration of DNA Double Helix from Wikipedia. Illustration showing stages of cell cycle: Interphase – portion of cell cycle in which the cell grows then replicates DNA. Mitosis – portion of cell cycle in which division of the cell takes place; includes Prophase, Metaphase, Anaphase, and Telaphase. Image courtesy of Wikepedia.

30 Illustration of DNA Double Helix from Wikipedia. Meiosis is the process of cell division that occurs in reproductive cells (sperm and egg). In this type of division, the chromosome number is halved from the diploid number (2n) to the haploid number (n).

31 Illustration of DNA Double Helix from Wikipedia. If gametes were diploid cells, the number of chromosomes would double with each generation. Meiosis ensures that gametes receive only one-half the number of chromosomes that are present in parent cells.

32 Illustration of DNA Double Helix from Wikipedia. Fertilization Fertilization is the process of joining the male gamete with the female gamete. Photo from Wikipedia.

33 Illustration of DNA Double Helix from Wikipedia. All animals originate from the union of a single haploid cell from the female (ovum or egg) and a single haploid cell from the male (spermatozoa or sperm). The result of this union is a zygote (diploid cell), which develops into a new animal with a full set of chromosomes.

34 Illustration of DNA Double Helix from Wikipedia. When discussing different generations in genetics, the first generation is referred to as the parent or P generation. Their offspring are referred to as the first filial or F 1 generation. P X P F 1 F 1

35 Illustration of DNA Double Helix from Wikipedia. When individuals from the F 1 generation are mated with each other, their offspring are referred to as the F 2 generation. F 1 X F 1 F 2 F 2 F 2 F 2

36 Illustration of DNA Double Helix from Wikipedia. Principle of Dominance In animals, chromosomes are paired and, therefore, genes are paired. These paired genes code for the same trait, but they are not identical. They can have different forms, known as alleles.

37 Illustration of DNA Double Helix from Wikipedia. For example, sheep and cattle can be polled or horned. One gene codes for this trait and the two possible forms (alleles) of the gene are polled or horned. USDA photo from Wikipedia. Photo from IMS.

38 Illustration of DNA Double Helix from Wikipedia. A capital letter is used to denote the dominant form of the gene (P) and a small letter is used to denote the recessive form of the gene (p). In the example, the polled allele is dominant and is, therefore, denoted by P, while the horned allele is recessive and denoted by p.

39 Illustration of DNA Double Helix from Wikipedia. Because genes are paired, an animal can have three different combinations of the two alleles: PP, Pp, or pp.

40 Illustration of DNA Double Helix from Wikipedia. When both genes in a pair take the same form (PP or pp), the animal is referred to as being homozygous for that trait. An animal with a PP genotype is referred to as homozygous dominant. An animal with the pp genotype is referred to as homozygous recessive.

41 Illustration of DNA Double Helix from Wikipedia. If one gene in the pair is the dominant allele (P) and the other gene is the recessive allele (p), the animal is referred to as being heterozygous for that trait and its genotype is denoted as Pp.

42 Illustration of DNA Double Helix from Wikipedia. Genotype refers to the actual genetic makeup. Phenotype refers to the physical expression of the genes. If an animal has the allele combination PP, it will be polled. If the combination is pp, the animal will be horned.

43 Illustration of DNA Double Helix from Wikipedia. If it is a heterozygote, then genotypically the animal will have both traits (Pp), but phenotypically the animal will be polled because the polled allele (P) is the dominant form of the gene.

44 Illustration of DNA Double Helix from Wikipedia. Mendel’s principle of dominance states that in a heterozygote, one allele may conceal the presence of another.

45 Illustration of DNA Double Helix from Wikipedia. In this example, the polled allele is concealing the horned allele and, therefore, is referred to as the dominant allele.

46 Illustration of DNA Double Helix from Wikipedia. Principle of Segregation When animals reproduce, they only pass on half of their genetic material to their offspring because gametes, or reproductive cells, only have one chromosome from each pair. The offspring will only receive one allele from each parent.

47 Illustration of DNA Double Helix from Wikipedia. The Principle of Segregation explains some of the differences that are observed in successive generations of animals and can be used to predict the probability of different combinations of alleles occurring in offspring.

48 Illustration of DNA Double Helix from Wikipedia. As previously discussed, three kinds of individuals are possible when describing a pair of genes: Homozygous dominant (PP), Homozygous recessive (pp), and Heterozygous (Pp).

49 Illustration of DNA Double Helix from Wikipedia. Considering these three types of individuals, six combinations of the various genotypes are possible: PP x PP (both parents are homozygous polled), PP x Pp (one homozygous polled parent and one heterozygous polled parent),

50 Illustration of DNA Double Helix from Wikipedia. PP x pp (one homozygous polled parent and one homozygous horned parent), Pp x Pp (both parents are heterozygous polled), Pp x pp (one heterozygous polled parent and one homozygous horned parent), and

51 Illustration of DNA Double Helix from Wikipedia. pp x pp (both parents are homozygous horned). The genotypes of the parents can be used to predict the phenotypes of the offspring.

52 Illustration of DNA Double Helix from Wikipedia. Predicting the Genotypes and Phenotypes of Offspring A punnett square is a grid-like method that is used to display and predict the genotypes and phenotypes of offspring from parents with specific alleles.

53 Illustration of DNA Double Helix from Wikipedia. The male genotype is normally indicated at the top and the female genotype is indicated in the vertical margin.

54 Illustration of DNA Double Helix from Wikipedia. When crossing homozygous dominant parents (PP x PP), all offspring will be homozygous dominant polled individuals.

55 Illustration of DNA Double Helix from Wikipedia. When crossing homozygous recessive parents (pp x pp), all of the offspring will be horned (homozygous recessive) individuals.

56 Illustration of DNA Double Helix from Wikipedia. When crossing a heterozygous parent with a homozygous dominant parent (Pp x PP), the expected offspring would occur in a 1:1 ratio of homozygous dominant to heterozygous individuals. Phenotypically, all offspring would be polled.

57 Illustration of DNA Double Helix from Wikipedia. When crossing a homozygous dominant parent with a homozygous recessive parent (PP x pp), all offspring would be heterozygous and polled.

58 Illustration of DNA Double Helix from Wikipedia.

59 When crossing a heterozygous parent with a homozygous recessive parent (Pp x pp), the offspring would occur in a genotypic ratio of 1:1 for heterozygous to homozygous recessive. About one-half of the offspring would be polled.

60 Illustration of DNA Double Helix from Wikipedia.

61 If two heterozygous parents are crossed (Pp x Pp), one can expect a genotypic ratio of 1:2:1, with one homozygous dominant polled, two heterozygous polled, and one homozygous recessive horned individuals. The expected phenotypic ratio of offspring would be 3:1 (polled to horned).

62 Illustration of DNA Double Helix from Wikipedia.

63 Considering Multiple Traits Commonly, there are multiple traits that need to be considered when mating animals. For example, consider that cattle can be horned or polled and white-faced or red-faced. The horns and red-faced coloring are recessive traits.

64 Illustration of DNA Double Helix from Wikipedia. If two individuals with two pairs of heterozygous genes (each affecting a different trait) are mated, the expected genotypic and phenotypic ratios would be: Genotypes – 1 PPWW, 2 PPWw, 2 PpWW, 4 PpWw, 1 PPww, 2 Ppww, 1 ppWW, 2 ppWw, and 1 ppww;

65 Illustration of DNA Double Helix from Wikipedia. Phenotypes – 9 polled, white- faced; 3 polled, red-faced; 3 horned, white-faced; and 1 horned, red-faced offspring.

66 Illustration of DNA Double Helix from Wikipedia.

67 The Law of Independent Assortment When considering multiple traits, Mendel hypothesized that genes for different traits are separated and distributed to gametes independently of one another.

68 Illustration of DNA Double Helix from Wikipedia. Therefore, when considering polled and white-faced traits, Mendel assumed that there was no relationship between how they were distributed to the next generation.

69 Illustration of DNA Double Helix from Wikipedia. In most cases, genes do assort independently. However, advances in genetics have shown that an abnormal situation, called crossing-over, can occur between genes for different traits.

70 Illustration of DNA Double Helix from Wikipedia. Crossing-over is an exchange of genes by homologous chromosomes during the synapses of meiosis prior to the formation of the sex cells or gametes. Thomas Hunt Morgan’s illustration (1916) courtesy of Wikipedia.

71 Illustration of DNA Double Helix from Wikipedia. Other Concepts in Genetics Non-traditional inheritance involves alleles that are not dominant or recessive. Incomplete, or partial dominance, and co-dominance are two examples of non-traditional inheritance.

72 Illustration of DNA Double Helix from Wikipedia. Partial (Incomplete) Dominance Partial, or incomplete, dominance occurs when the heterozygous organism exhibits a trait in-between the dominant trait and the recessive trait.

73 Illustration of DNA Double Helix from Wikipedia. Partially dominant alleles for color are seen in several species of flowers and in mice. Ex. Homozygous mice are black (BB) or white (bb) and the heterozygous mice will be grey (Bb).

74 Illustration of DNA Double Helix from Wikipedia. Sheep exhibit incomplete dominance in the trait for eye color. When a pure, brown-eyed sheep is crossed with a pure, green-eyed sheep, blue-eyed offspring are produced.

75 Illustration of DNA Double Helix from Wikipedia. Codominance Codominance occurs when a heterozygote offspring exhibits traits found in both associated homozygous individuals. An example of codominance is the feather color of chickens.

76 Illustration of DNA Double Helix from Wikipedia. If a homozygous black rooster is mated to a homozygous white hen, the heterozygous offspring would have both black feathers and white feathers.

77 Illustration of DNA Double Helix from Wikipedia. Roan is a coat color in horses (sometimes dogs and cattle) that is a mixture of base coat colored hairs (ex. black, chestnut) and white hairs. Neither the base coat color or the white hairs are dominant nor do they blend to create an intermediate color.

78 Illustration of DNA Double Helix from Wikipedia. The roan animal actually has both colored and white hairs. Photo courtesy of Wikipedia.

79 Illustration of DNA Double Helix from Wikipedia. Under these circumstances, neither allele is dominant and neither is recessive. Therefore, each allele is denoted by a capital letter.

80 Illustration of DNA Double Helix from Wikipedia. Epistasis (Polygenic Inheritance) It is possible for more than one gene to control a single trait. This type of interaction between two nonallelic genes is referred to as epistasis.

81 Illustration of DNA Double Helix from Wikipedia. When two or more genes influence a trait, an allele of one of them may have an epistatic, or overriding, effect on the phenotype. Comb shape in chickens is an example of an epistatic relationship.

82 Illustration of DNA Double Helix from Wikipedia. Domestic chickens can have four different types of comb shapes: (a) rose, (b) pea, (c) walnut, and (d) single.

83 Illustration of DNA Double Helix from Wikipedia. Comb shape is influenced by two independently assorting genes, R and P, each with two alleles. Wyandotte chickens with rose combs have the genotype RRpp,while the Brahma chickens with pea combs have the genotype rrPP.

84 Illustration of DNA Double Helix from Wikipedia. The F 1 hybrids between these two varieties are RrPp; phenotypically, they have walnut combs. If those hybrids are intercrossed with each other, all four types of combs appear in the progeny in a ratio of 9:3:3:1 for walnut:rose:pea:single.

85 Illustration of DNA Double Helix from Wikipedia.

86 Mutations and Other Chromosomal Abnormalities Genes have the capability of duplicating themselves, but sometimes a mistake is made in the duplication process resulting in a mutation.

87 Illustration of DNA Double Helix from Wikipedia. The new gene created by this mutation will cause a change in the code sent by the gene to the protein formation process. Some mutations cause defects in animals, while others may be beneficial.

88 Illustration of DNA Double Helix from Wikipedia. Mutations are responsible for variations in coat color, size, shape, behavior, and other traits in several species of animals. The beneficial mutations are helpful to breeders trying to improve domestic animals.

89 Illustration of DNA Double Helix from Wikipedia. Changes that can occur in chromosomes during meiosis include: Nondisjunction – chromosome number, Translocation or deletion – chromosome breakage, and Inversion – the rearrangement of genes on a chromosome.

90 Illustration of DNA Double Helix from Wikipedia. Changes in chromosomes are reflected in the phenotypes of animals. Some chromosomal changes will result in abnormalities, while others are lethal and result in the death of an animal shortly after fertilization, during prenatal development, or even after birth.

91 Illustration of DNA Double Helix from Wikipedia. Sex-Linked Traits Sex-linked traits involve genes that are carried only on the X or Y chromosomes, which are involved in determining the sex of animals. The female genotype is XX, while the male genotype is XY.

92 Illustration of DNA Double Helix from Wikipedia. The X chromosome is larger and longer than the Y chromosome, which means a portion of the X chromosome does not pair with genes on the Y chromosome.

93 Illustration of DNA Double Helix from Wikipedia. Additionally, a certain portion of the Y chromosome does not link with the X chromosome. The traits on this portion of the Y chromosome are transmitted only from fathers to sons. Sex-linked traits are often recessive and are covered up in the female mammal by dominant genes.

94 Illustration of DNA Double Helix from Wikipedia. The expression of certain genes, which are carried on the regular body chromosomes of animals, is also affected by the sex of the animal. The sex of an animal may determine whether a gene is dominant or recessive (Ex. Scurs in polled European cattle).

95 Illustration of DNA Double Helix from Wikipedia. In poultry, the male has the genotype XX, while the female has the genotype Xw. An example of a sex-linked trait in poultry is the barring of Barred Plymouth Rock chickens.

96 Illustration of DNA Double Helix from Wikipedia. If barred hens are mated to non-barred males, all of the barred chicks from this cross are males, and the non-barred chicks are females. Photo courtesy of Wikipedia.

97 Illustration of DNA Double Helix from Wikipedia. Genetic Selection Permanent improvements in domestic animals can be made by genetic selection through natural or artificial means. Natural selection occurs in wild animals, while artificial selection is planned and controlled by humans.

98 Illustration of DNA Double Helix from Wikipedia. Animals that exhibit desirable traits are selected and mated. Animals that exhibit undesirable traits are not allowed to reproduce or are culled from the herd. “Geneticist Michael MacNeil examines results from genetic analysis of sires used in the Angus Sire Alliance program at Circle A Angus Ranch. Economic values for individual traits are used to sort bulls by potential profitability of their offspring” (USDA – ARS). Photo by Peggy Greb courtesy of USDA Agricultural Research Service.

99 Illustration of DNA Double Helix from Wikipedia. The goal of selection is to increase the number of animals with optimal levels of performance, while culling individuals with poorer performance. Genetic improvement is a slow process and can take several generations to see an improvement in a trait.

100 Illustration of DNA Double Helix from Wikipedia. Artificial insemination and embryo transfer are breeding methods that are commonly used to decrease the time taken to improve a trait. “Angus surrogate mother nurses her Romosinuano embryo transfer calf. Initially, scientists are investigating the influence of surrogate breed on Romosinuano calf traits such as length of gestation and birth and weaning weights” (USDA-ARS) Photo by Scott Bauer courtesy of USDA Agricultural Research Service.

101 Illustration of DNA Double Helix from Wikipedia. Traits are passed from parents to offspring, but some traits are more heritable than other traits. That is, the genotype of an individual will be expressed more strongly and environment will be less influential for particular traits.

102 Illustration of DNA Double Helix from Wikipedia. TraitSheepSwineCattle Weaning weight15-25%15-20%15-27% Post-weaning gain efficiency 20-30% 40-50% Post-weaning rate of gain50-60%25-30%50-55% Feed efficiency50%12%44% Loin eye area53% 56% Heritability of Various Traits in Livestock

103 Illustration of DNA Double Helix from Wikipedia. Several genes influence some traits. For example, rate of growth is a trait that is influenced by appetite, energy expenditure, feed efficiency, and body composition. Photo by Brian Prechtel courtesy of USDA Agricultural Research Service.

104 Illustration of DNA Double Helix from Wikipedia. Breeding systems aim to improve a single trait or multiple traits. Single trait selection – aimed at improving one trait in a breeding program with little or no regard for improvement in other (associated) traits.

105 Illustration of DNA Double Helix from Wikipedia. Multiple trait selection – aims to simultaneously improve a number of traits. Theoretically, multiple trait selection should result in a faster rate of gain toward a specific objective.

106 Illustration of DNA Double Helix from Wikipedia. Most domestic species now have a recognized system in place that allows breeders to estimate the genetic merit of individuals. In the United States, cattle, sheep, goat, and swine breeders use expected progeny differences (EPDs).

107 Illustration of DNA Double Helix from Wikipedia. EPDs are used to compare animals from the same species and breed. “Newly developed EPDs (expected progeny differences) make it possible to select for tenderness and carcass and beef quality traits in Brahman cattle, shown here at the ARS Subtropical Agricultural Research Station in Brooksville, Florida” (USDA-ARS). Photo by David Riley courtesy of USDA Agricultural Research Service.

108 Illustration of DNA Double Helix from Wikipedia. For EPD values to be used effectively, one needs to know the breed averages, the accuracy of the EPDs, and who estimated the EPDs. A high EPD is not necessarily good; it depends on the trait being considered and breeding objectives.

109 Illustration of DNA Double Helix from Wikipedia. Modern Genetics In recent years, traditional methods of improvement through selection and breeding have been superceded by genetic manipulation. A substantial amount of research has focused on direct manipulation of genes and DNA.

110 Illustration of DNA Double Helix from Wikipedia. Gene Transfer Genetic engineering basically refers to transferring a gene from one individual to another.

111 Illustration of DNA Double Helix from Wikipedia. Scientists are able to code genes for desirable compounds and insert them into other cells, such as microorganisms. These microorganisms produce these desirable compounds on a large scale.

112 Illustration of DNA Double Helix from Wikipedia. This area of genetic manipulation makes important contributions to domesticated animals in relation to immunology, vaccines, aging, and cancer. “Annie the cow: bioengineered to have a gene for mastitis resistance” (USDA- ARS). Photo by Scott Bauer courtesy of USDA Agricultural Research Service.

113 Illustration of DNA Double Helix from Wikipedia. The implications for introducing superior production, conformation, and disease- resistant traits into domestic animals through gene transfer hold considerable promise in the genetic improvement of animals.

114 Illustration of DNA Double Helix from Wikipedia. Cloning Embryonic cloning of animals involves the chemical or surgical splitting of developing embryos shortly after fertilization and, consequently, developing two identical individuals.

115 Illustration of DNA Double Helix from Wikipedia. The separated embryos are allowed to culture, or grow, to a more advanced embryonic stage before they are implanted into the uterus of a recipient mother for full development.

116 Illustration of DNA Double Helix from Wikipedia. Embryonic cloning has been performed successfully in several species of animals.

117 Illustration of DNA Double Helix from Wikipedia. Nuclear Transfer Nuclear transfer is another method of cloning that involves the microsurgical collection of nuclear material from a donor cell which is then transferred into an unfertilized ovum that has had its own nucleus removed.

118 Illustration of DNA Double Helix from Wikipedia. The cells that develop successfully become identical individuals. Dolly the Sheep (the first mammal cloned from adult cells) and many other species have been cloned this way. Photo courtesy of Wikipedia.

119 Illustration of DNA Double Helix from Wikipedia. Worldwide, the institute that has cloned the most species is Texas A&M University, College of Veterinary Medicine, which to date has cloned cattle, swine, a goat, a horse, deer, and a cat.

120 Illustration of DNA Double Helix from Wikipedia. Nuclear Fusion Another innovation in genetic engineering, called nuclear fusion, involves the union of nuclei from two gametes, male or female sex cells.

121 Illustration of DNA Double Helix from Wikipedia. This fusion shows promise for the uniting of nuclei from two outstanding females, two outstanding males, or the normal outstanding male and female combination.

122 Illustration of DNA Double Helix from Wikipedia. The possibility for selecting desired traits at the cellular level holds exciting implications for the genetic improvement of domestic animals.

123 Illustration of DNA Double Helix from Wikipedia. ALL RIGHTS RESERVED Reproduction or redistribution of all, or part, of this presentation without written permission is prohibited. Instructional Materials Service Texas A&M University 2588 TAMUS College Station, Texas


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