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CINVESTAV Unidad Irapuato

2011. Octubre 17 – Noviembre 18. CINVESTAV Unidad Irapuato. Genética y Biología Molecular I - 2011. Profesores. Dr. RUAIRIDH SAWERS. The Genotype–Phenotype Relationship. Dr. RICHARD A. JORGENSEN. Organization and Expression of Genes and Genomes. Dr. STEWART GILLMOR. Molecular genetics.

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CINVESTAV Unidad Irapuato

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  1. 2011 Octubre 17 – Noviembre 18 CINVESTAV Unidad Irapuato

  2. Genética y Biología Molecular I - 2011 Profesores Dr. RUAIRIDH SAWERS TheGenotype–PhenotypeRelationship Dr. RICHARD A. JORGENSEN Organization and Expression of Genes and Genomes Dr. STEWART GILLMOR Molecular genetics Dr. Luis Delaye Evolutionary genetics Invitada DrA. Angélica Cibrian ecological genomics

  3. Genética y Biología Molecular I - 2011 Octubre 17 – Noviembre 18

  4. Genética y Biología Molecular I - 2011 1 2 4 3

  5. Genética y Biología Molecular I - 2011 1 2 4 3 5 Genómica Ecológica

  6. Genética y Biología Molecular I - 2011 http://bioingenios.ira.cinvestav.mx:81/genomica-evolutiva/Gene/Genetics.html

  7. Genética y Biología Molecular I - 2011 http://bioingenios.ira.cinvestav.mx:81/genomica-evolutiva/Gene/Genetics.html

  8. Genética y Biología Molecular I - 2011 http://bioingenios.ira.cinvestav.mx:81/genomica-evolutiva/Gene/Genetics.html

  9. Genética y Biología Molecular I - 2011 http://bioingenios.ira.cinvestav.mx:81/genomica-evolutiva/Gene/Genetics.html

  10. Genética y Biología Molecular I - 2011 http://www.ira.cinvestav.mx:86/

  11. Genética y Biología Molecular I - 2011 Octubre 17 – Noviembre 18 Exámenes

  12. Genética y Biología Molecular I - 2011 Evaluación 25% 25% 25% 25% Ensayo

  13. Genética y Biología Molecular I - 2011 Idioma Dr. RUAIRIDH SAWERS Dr. RICHARD A. JORGENSEN Dr. STEWART GILLMOR Dr. Luis Delaye DrA. Angélica Cibrian

  14. Genética y Biología Molecular I - 2011 Últimas palabras Aprender genética NO es sencillo Un mes es MUY poco tiempo Estamos aquí para ayudarles pero requieren esforzarse para aprender Email: ldelaye@ira.cinvestav.mx

  15. MOLECULAR BIOLOGY AND GENETICS: SECTION 1

  16. Contents of CINVESTAV Molecular Biology Section I 1. The Mendelian Model 2. Linkage and genetic mapping 3. Questions of context 4. Quantitative variation An Introduction to Genetic Analysis Griffithset al. www.ncbi.nlm.nih.gov/books/NBK21766/ Ruairidh Sawers, Oct 2011

  17. Molecular Biology Section I: Articles to read • Mendel G. 1866. VersucheüberPlflanzenhybriden. Verhandlungendes naturforschendenVereines in Brünn, Bd. IV für das Jahr 1865, Abhandlungen, 3–47. • SchullGH. 1908. Composition of a maize field. American Breeders Assoc. Vol.II • Sax K. 1923. The association of size differences with seed-coat pattern and pigmentation in Phaseolus vulgaris. Genetics 8:552-560. • FraryA et al. 2000. fw2.2: a quantitative trait locus key to the evolution of tomato fruit size. Science 289: 85-8. • XuK. et al. 2006. Sub1A is an ethylene-response-factor-like gene that confers submergence tolerance to rice. Nature 442: 705-8. • HarjesCE et al. 2008. Natural genetic variation in lycopene epsilon cyclasetapped for maize biofortification. Science 319: 330-3. • KrattingerSG et al. 2009. A putative ABC transporter confers durable resistance to multiple fungal pathogens in wheat. Science 323: 1301-2. • Takeda S and Matsuoka M. 2008. Genetic approaches to crop improvement: responding to environmental and population changes. Nat Rev Genet. 9: 444-57 • Waugh R et al. 2009. The emergence of whole genome association scans in barley. CurrOpin Plant Biol. 12: 218-22. • JanninkJL et al. 2010. Genomic selection in plant breeding: from theory to practice. Brief Funct Genomics 9: 166-77. Ruairidh Sawers, Oct 2011

  18. The physiology of decent The term genetics (from the Greek genetikos - origin, fertile, productive) first popularized by William Bateson as the “Study of heredity and variation”. First formally used to “rename” the 1906 3rdInternational Conference on Hybridization and Plant Breeding as the 3rd International Conference on Genetics. “[Genetics] sufficiently indicates that our labours are devoted to the elucidation of the phenomena of heredity and variation: in other words, the physiology of Decent.” William Bateson, 1906 Ruairidh Sawers, Oct 2011

  19. 1. The Mendelian Model Irapuato, 17th October 2011

  20. Lecture 1: The Mendelian Model 1. Revision of basic terminology [modern usage] 2. Mendel’s model and “laws” [modern synthesis] 3. “VersucheüberPflanzenhybriden” (1865) 4. Testing Mendelian ratios: χ2 The Monk in the Garden Robin Henig Houghton (New York), 2000 Ruairidh Sawers, Oct 2011

  21. Revision of basic terminology 1 Gene: The fundamental unit of heredity Gamete: A specialized haploid cell that fuses with a gamete from the opposite sex or mating type to form a diploid zygote Genotype: The specific allelic composition of a cell – either of the entire cell or for a certain gene or set of genes Heterozygote: An individual having a gene pair of different alleles in the two chromosome sets of the diploid individual Homozygote:An individual having a gene pair of identical alleles in the two chromosome sets of the diploid individual Hybrid: 1) A heterozygote. 2) A progeny individual from any cross involving parents of different genotypes Ruairidh Sawers, Oct 2011

  22. Revision of basic terminology 2 Allele: One of the different forms of a gene that exist at a single locus Dominant allele: Form expressed even when heterozygous with a second recessive allele Monohybrid cross: Cross between two individuals identically heterozygous at a single locus Dihybrid cross: Cross between two individuals identically heterozygous at a two loci Backcross: Cross between hybrid progeny and either of their parents F1: First filial generation, produced by crossing two parental lines F2: Second filial generation, produced by selfing or intercrossing of F1 Ruairidh Sawers, Oct 2011

  23. Mendel’s Model of Heredity: Monohybrid cross Parents (P) AA x aa A a Gametes Aa Filial 1 (F1) x 3A:1a F2 Ratio (Phenotypic) Ruairidh Sawers, Oct 2011

  24. Mendel’s Model of Heredity (Modern synthesis) 1.The existence of genes. There are hereditary determinants of a particulate nature. We now call these determinants genes. 2.Genes are in pairs. Alternative phenotypes of a character are determined by different forms of a single type of gene. The different forms of one type of gene are called alleles. 3.The principle of segregation. The members of the gene pairs segregate (separate) equally into the gametes, or eggs and sperm. 4.Gametic content. Consequently, each gamete carries only one member of each gene pair. 5.Random fertilization. The union of one gamete from each parent to form the first cell (zygote) of a new progeny individual is random. Ruairidh Sawers, Oct 2011

  25. Mendel’s “Laws” Mendel’s 1st Law The two members of a gene pair segregate from each other into the gametes, so that one-half of the gametes carry one member of the pair and the other one-half of the gametes carry the other member of the pair. Mendel’s 2nd Law During gamete formation the segregation of alleles of one gene is independent of the segregation of alleles of another gene Ruairidh Sawers, Oct 2011

  26. Mendel’s Model of Heredity: Dihybrid cross Parents (P) AABB x aabb AB ab Gametes AaBb Filial 1 (F1) x 9AB:3Ab:3aB:1ab F2 Ratio (phenotypic) Ruairidh Sawers, Oct 2011

  27. Whether the plan upon which the separate experiments were …carried out was the best suited to attain the desired end is left to the friendly decision of the reader. Gregor Mendel, Verhandlungendes naturforschenden Vereines in Brünn, 1865

  28. “Experiments in plant hybridization” (1865) Gregor Mende. 1866. Versuche über Plflanzenhybriden. Verhandlungen des naturforschenden Vereines in Brünn, Bd. IV für das Jahr 1865, Abhandlungen, 3–47. Ruairidh Sawers, Oct 2011

  29. Mendel’s experimental system “The experimental plants must necessarily: 1. Possess constant differentiating characteristics 2. The hybrids of such plants must, during the flowering period, be protected from the influence of all foreign pollen, or be easily capable of such protection.” “The experimental plants must necessarily: 1. Possess constant differentiating characteristics Ruairidh Sawers, Oct 2011

  30. Mendel’s “Merkmale” “The experimental plants must necessarily possess constant differentiating characteristics” “Die Versuchspflanzenmüssennothwendig constant differirendeMerkmalebesitzen” Merkmale has connotations of both genotype and phenotype; they are at once the determinants and expressions of heredity Genotype Phenotype Ruairidh Sawers, Oct 2011

  31. Mendel’s Choice of Traits Ruairidh Sawers, Oct 2011

  32. Dominance in Mendel’s F1 “Henceforth in this paper those characters which are transmitted entire, or almost unchanged in the hybridization, and therefore in themselves constitute the characters of the hybrid, are termed the dominant, and those which become latent in the process recessive.” Ruairidh Sawers, Oct 2011

  33. Segregation in Mendel’s F2: the first “law” “In this generation there reappear, together with the dominant characters, also the recessive ones with their peculiarities fully developed, and this occurs in the definitely expressed average proportion of three to one, so that among each four plants of this generation three display the dominant character and one the recessive.” Ruairidh Sawers, Oct 2011

  34. Der doppelteBedeutungdes Merkmales “The dominant character can have here a double signification –– viz. that of a parental character or a hybrid–character. In which of the two significations it appears in each separate case can only be determined by the following generation.” i.e. the Genotype-Phenotype correspondence breaks down; the dominant Merkmalis split into an observable portion and a latent, yet transmissible, portion Genotype Phenotype Genotype 1 Phenotype 1 Genotype 2 Phenotype 2 Ruairidh Sawers, Oct 2011 Genotype 3

  35. Mendel’s Dihybrids: The second “law” Parents (P) x wrinkled/green Round/Yellow Round/Yellow Filial 1 (F1) x 9:3:3:1 F2 Ratio (phenotypic) Ruairidh Sawers, Oct 2011

  36. Mendel’s Dihybrids: The second “law” Parents (P) AABB x aabb AB ab Gametes AaBb Filial 1 (F1) x 9AB:3Ab:3aB:1ab F2 Ratio (phenotypic) Ruairidh Sawers, Oct 2011

  37. Mendel’s Dihybrids: The second “law” Parents (P) AABB x aabb AB ab Gametes AaBb Filial 1 (F1) x 9AB:3Ab:3aB:1ab F2 Ratio (phenotypic) Ruairidh Sawers, Oct 2011

  38. Mendel’s Backcross: Revealing the gametes Parents (P) x wrinkled/green Round/Yellow x Round/Yellow wrinkled/green Filial 1 (F1) 1:1:1:1 BC1 Ratio (phenotypic) Ruairidh Sawers, Oct 2011

  39. Mendel’s Backcross: Revealing the gametes Parents (P) x aabb AABB x AaBb aabb Filial 1 (F1) 1:1:1:1 BC1 Ratio (phenotypic) Ruairidh Sawers, Oct 2011

  40. Mendel’s Backcross: Revealing the gametes Parents (P) x aabb AABB x AaBb aabb Filial 1 (F1) 1:1:1:1 BC1 Ratio (phenotypic) Ruairidh Sawers, Oct 2011

  41. The χ2 distribution In practice, data will never exactly follow Mendelian ratios We can obtain expectations and test for concordance using χ2 For segregation data, the test statistic: X2 = ≈ χ2 where expected values are derived as the exact Mendelian ratios As phenotypic counts are discrete, the test statistic X2 is only approximately distributed as χ2 A (somewhat questionable!) rule-of-thumb, states that this is only a problem for small expected values (<5) Ruairidh Sawers, Oct 2011

  42. Testing patterns of segregation Data from Bateson and Punnett on flower colour and pollen grain shape in sweet pea Parents: Purple/Long and red/round; segregation in the F2: X2 = + Ruairidh Sawers, Oct 2011

  43. The χ2 table (3d.f.) Use χ2 table to convert test values to probabilities With a 2 x 2 contingency table, test on 3 degrees of freedom (d.f.) values of X2 up to 7.82 can be considered a good fit obs to exp i.e. we expect such values >5% of the time “by chance” The sweet pea value of X2 ≈ 94 ,is a clear deviation from the Mendelian ratio Ruairidh Sawers, Oct 2011

  44. The Mendelian school: 1900 William Bateson Hugo de Vries Karl Correns Ruairidh Sawers, Oct 2011

  45. Summary

  46. Revision of basic terminology 1 Gene: The fundamental unit of heredity Gamete: A specialized haploid cell that fuses with a gamete from the opposite sex or mating type to form a diploid zygote Genotype: The specific allelic composition of a cell – either of the entire cell or for a certain gene or set of genes Hybrid: 1) A heterozygote. 2) A progeny individual from any cross involving parents of different genotypes Heterozygote: An individual having a gene pair of different alleles in the two chromosome sets of the diploid individual Homozygote:An individual having a gene pair of identical alleles in the two chromosome sets of the diploid individual Ruairidh Sawers, Oct 2011

  47. Revision of basic terminology 2 Allele: One of the different forms of a gene that exist at a single locus Dominant allele: Form expressed even when heterozygous with a second recessive allele Monohybrid cross: Cross between two individuals identically heterozygous at a single locus Dihybrid cross: Cross between two individuals identically heterozygous at a two loci Backcross: Cross between hybrid progeny and either of the parents F1: First filial generation, produced by crossing two parental lines F2: Second filial generation, produced by selfing or intercrossing of F1 Ruairidh Sawers, Oct 2011

  48. Mendel’s Model of Heredity 1.The existence of genes. There are hereditary determinants of a particulate nature. We now call these determinants genes. 2.Genes are in pairs. Alternative phenotypes of a character are determined by different forms of a single type of gene. The different forms of one type of gene are called alleles. 3.The principle of segregation. The members of the gene pairs segregate (separate) equally into the gametes, or eggs and sperm. 4.Gametic content. Consequently, each gamete carries only one member of each gene pair. 5.Random fertilization. The union of one gamete from each parent to form the first cell (zygote) of a new progeny individual is random. Ruairidh Sawers, Oct 2011

  49. Mendel’s “Laws” Mendel’s 1st Law The two members of a gene pair segregate from each other into the gametes, so that one-half of the gametes carry one member of the pair and the other one-half of the gametes carry the other member of the pair. Mendel’s 2nd Law During gamete formation the segregation of alleles of one gene is independent of the segregation of alleles of another gene Ruairidh Sawers, Oct 2011

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