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Fundamental Principles of Genetics

Fundamental Principles of Genetics. Genetics – study of heredity Gene – determinant of heredity Chapter is outline of basic principles of genetics. Cell Theory of Inheritance. Plants and animals composed of cells Plant cell – surrounded by cell wall Animal cell – surrounded by cell membrane

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Fundamental Principles of Genetics

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  1. Fundamental Principles of Genetics • Genetics – study of heredity • Gene – determinant of heredity • Chapter is outline of basic principles of genetics

  2. Cell Theory of Inheritance • Plants and animals composed of cells • Plant cell – surrounded by cell wall • Animal cell – surrounded by cell membrane • Nucleus – location of chromosomes in cell • Chromosomes – carrier of genes

  3. Chromosomes • Carriers of genetic material – genes • Occur in pairs • Homologous chromosomes – members of a pair • Number of chromosomes constant among normal members of a species

  4. Chromosome Number • Diploid (2N) numbers • donkey 62 horse 64 • mule 63 swine 38 • sheep 54 cattle 60 • human 46 mink 30 • dog 78 cat 38 • chicken 78 • Normal cells have diploid (2N) number • Gametes (sperm and egg) have haploid (1N) number

  5. Chromosomes • Two major types • Sex chromosomes – one pair which influences sex of organism • Autosomes – all pairs other than sex chromosomes

  6. Sex Determination • Mammals • Sex chromosomes are: • female XX homogametic • male XY heterogametic • Chickens and turkeys • Sex chromosomes are: • female ZW heterogametic • male ZZ homogametic

  7. Chromosomal Abnormalities • Changes in number of chromosomes • Aneuploidy – extra or missing chromosome • Polyploidy – extra or missing sets of chromosomes • Usually lethal in animals • Except aneuploidy of very small chromosomes (eg Down Syndrome in humans is extra #21)

  8. Chromosomal Abnormalities • Changes in chromosome structure • Deletion – piece of chromosome removed • Duplication – piece of chromosome duplicated • Translocation – exchange of material between different chromosomes • Inversion – segment of chromosome reversed

  9. Chromosomal Abnormalities • Changes in chromosome structure • Cause loss of fertility • Amount of loss dependent on type of change and importance of the affected segment of the chromosome

  10. Cell Division • Two types • Mitosis – division of normal body cells • Results in production of two identical diploid cells • Meiosis – division of germinal cells to produce gametes (sperm and egg) • -Results in production of four different haploid cells

  11. Cell Division • Mitosis • Cell division of normal body cells • Each daughter cell has same genetic complement as original cell

  12. Cell Division • Mitosis • Four phases • Prophase – Chromosomes become visible • Metaphase – Chromosomes line up across cell center • Anaphase – Sister chromatids separate • Telophase – Chromosomes condense and new nucleus is formed • Interphase – period between cell divisions • Cytokinesis – the actual division of the cell

  13. 18. G2 Phase – Preparation 19. Prophase 20. Metaphase 21. Anaphase 22. Telophase 23. Cytokinesis 24. G1 Phase - Cell Growth 25. S Phase - Replication Mitosis

  14. Mitosis -- Meiosis

  15. Cell Division • Meiosis • Division in germinal cells to produce sperm and egg • Each cell that results has 1N number of chromosomes (half of number of chromosomes in body cells

  16. Cell Division • Meiosis • Two cycles of: • Prophase • Metaphase • Anaphase • Telophase • Results in four cells with 1N number

  17. Cell Division • Meiosis • Spermatogenesis – meiotic production of sperm cells • Oogenesis – meiotic production of egg cells

  18. The Gene • Composed of DNA – deoxyribonucleic acid • Large double stranded polymer of units called nucleotides • Nucleotide • Sugar – deoxyribose • Phosphate group • Nitrogeneous base • adenine guanine • cytosine thymine

  19. DNAhttp://www.youtube.com/watch?v=qy8dk5iS1f0http://www.youtube.com/watch?v=hfZ8o9D1tushttp://www.youtube.com/watch?v=OtYz_3rkvPkDNAhttp://www.youtube.com/watch?v=qy8dk5iS1f0http://www.youtube.com/watch?v=hfZ8o9D1tushttp://www.youtube.com/watch?v=OtYz_3rkvPk

  20. Transcription of RNA • Bases in DNA code for transcription of RNA • RNA – ribonucleic acid • Also nucleic acid • Single stranded • Uracil instead of thymine • Ribose instead of deoxyribose

  21. RNA • Three primary types of RNA • Messenger RNA • Transfers code from DNA to protein synthesis • Transfer RNA • Carries amino acids to the ribosome • Ribosomal RNA • Forms part of the structure of the ribosome

  22. Genetic Code • Each amino acid coded by a three base sequence (codon) • Most amino acids have more than one codon • One codon specifies beginning of a protein • Three codons specify the end of a protein

  23. Interactions Between Genes • Epistasis • Two or more gene pairs in which one gene pair influences expression of another gene pair • Horned, polled, scurred • Two gene pairs (horned vs polled) (smooth vs scurred) • If horned – scurred vs smooth does not matter • If polled – scurred vs smooth can express

  24. Genes and Embryological Development • After union of sperm and egg • Cell division occurs • Early development - all cells are alike • Subsequent development – cells differentiate • Embryological development is genetically controlled

  25. Genes and Embryological Development • Lethal genes • Genes which stop development • Many must be received from both parents to cause death • Cause of high percentage of embryonic death

  26. Biotechnology • Biotechnology • All technologies that pertain to molecular manipulation of living material • Very difficult word to characterize • Genetic engineering • New methods for modifying the animal genome

  27. Transgenesis • Transgenesis • Movement of genes from one species into another • First use – development of mouse with extra genes for growth hormone

  28. Genetic Engineering in Plants • Round-up-ready crops • Several crop species have been engineered to be resistant to the herbicide Round-up • Bt crops • Corn and cotton have genes from a microbe that causes them to be resistant to corn borer and boll weevil • Flavr-Savr tomato • Gene altered to lengthen shelf life

  29. Cloning • Clone – genetic identical • Identical twins are clones • Cloning by embryo splitting has been available for several years • Cloning from an adult DNA donor not possible until “Dolly”

  30. Cloning • Dolly • Developed at Roslin Institute • Sheep cloned from cells from adult ewe mammary gland • Cells had to be “started over” to remove results of cell differentiation

  31. Cloning • Potential uses for cloning in animals • Limited importance in routine livestock improvement • Combine with transgenesis to produce animals with unique genetic makeup • transgenesis to create first copy of animal with specific gene inserted • cloning to make multiple copies of that animal

  32. Marker Assisted Selection • Current selection • Based on actual traits measured in animals • Marker assisted selection • Based on identification of genetic markers that are associated with performance traits • Can be applied as soon as appropriate tissue (blood, skin etc) can be obtained • Shortens time to obtain information for choosing superior parents

  33. Mutation • Mutation – change in the base sequence • May result in change in amino acid sequence in protein • May result in change in the phenotype • Change is usually detrimental • Only source of new genetic material

  34. Phenotypic Expression of Genes • Phenotype = Genotype + Environment • Gene action varies among different genes • Dominance relationships vary widely

  35. Dominant and recessive • Color in Angus • Genotype Phenotype • BB Black • Bb Black • bb Red • Black is dominant to red • Red is recessive • BB or bb – homozygous • Bb - heterozygous Phenotypic Expression of Genes

  36. Phenotypic Expression of Genes • Lack of dominance • Color in Shorthorns • Genotype Phenotype • BB Red • Bb Roan • bb White • Both red and white are expressed in heterozygote

  37. Sex-linked Inheritance • Some genes on the sex chromosomes • Inheritance pattern affected because males have only one X chromosome • Hemophilia in humans • Deficiency in ability for blood to clot

  38. Sex-influenced Inheritance • Inheritance that is affected by sex of individual • eg. scurs - dominant in males, recessive in females • eg. horns in sheep – dominant in males, recessive in females

  39. Sex-limited Inheritance • Some traits express in only one sex • Female • Milk production, egg production, age at first estrus • Male • Scrotal circumference

  40. Genome Project • Human Genome project • Initiated by National Institutes of Health and Department of Energy • Large multi-year, multi-location project to map the human genome • Other genome projects • Cattle, sheep, swine, horses, dogs, cats, turkeys, chickens, mice and many other species

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