1 Mendelian Genetics 2 Gregor Mendel (1822-1884) Responsible for the Laws governing Inheritance of Traits.

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<ul><li> Slide 1 </li> <li> Slide 2 </li> <li> 1 Mendelian Genetics </li> <li> Slide 3 </li> <li> 2 Gregor Mendel (1822-1884) Responsible for the Laws governing Inheritance of Traits </li> <li> Slide 4 </li> <li> 3 Gregor Johann Mendel Austrian monk Studied the inheritance of traits in pea plants Developed the laws of inheritance Mendel's work was not recognized until the turn of the 20th century </li> <li> Slide 5 </li> <li> 4 Gregor Johann Mendel Between 1856 and 1863, Mendel cultivated and tested some 28,000 pea plants He found that the plants' offspring retained traits of the parents Called the Father of Genetics" </li> <li> Slide 6 </li> <li> 5 Site of Gregor Mendels experimental garden in the Czech Republic </li> <li> Slide 7 </li> <li> 6 Mendel stated that physical traits are inherited as particles Mendel did not know that the particles were actually Chromosomes &amp; DNA Particulate Inheritance </li> <li> Slide 8 </li> <li> 7 Genetic Terminology Trait - any characteristic that can be passed from parent to offspring Heredity - passing of traits from parent to offspring Genetics - study of heredity </li> <li> Slide 9 </li> <li> 8 Designer Genes Alleles one of the two forms of a gene (dominant &amp; recessive) Dominant - stronger of two genes expressed in the hybrid; represented by a capital letter (R) Recessive - gene that shows up less often in a cross; represented by a lowercase letter (r) </li> <li> Slide 10 </li> <li> 9 Genetic Terminology Monohybrid - cross involving a single trait e.g. flower color Dihybrid cross involving two traits e.g. flower color &amp; plant height True Breeding True Breeding all offspring will have the same characteristic generation after generation </li> <li> Slide 11 </li> <li> 10 Genotypes Homozygous genotype - gene combination involving 2 dominant or 2 recessive genes (e.g. RR or rr); also called pure Homozygous genotype - gene combination involving 2 dominant or 2 recessive genes (e.g. RR or rr); also called pure Heterozygous genotype - gene combination of one dominant &amp; one recessive allele (e.g. Rr); also called hybrid </li> <li> Slide 12 </li> <li> 11 More Terminology Genotype - gene combination for a trait (e.g. RR, Rr, rr) Phenotype - the physical feature resulting from a genotype (e.g. red, white) </li> <li> Slide 13 </li> <li> 12 Genotype &amp; Phenotype in Flowers Genotype of alleles: R = red flower r = yellow flower All genes occur in pairs, so 2 alleles affect a characteristic Possible combinations are: GenotypesRR Rrrr PhenotypesRED RED YELLOW </li> <li> Slide 14 </li> <li> 13 Genotypes Parental Generation (P1) - Parental Generation (P1) - the parental generation in a breeding experiment First Filial generation (F1) First Filial generation (F1) First generation created by parents Second Filial generation (F2) - the second-generation offspring in a breeding experiment. </li> <li> Slide 15 </li> <li> 14 Mendels Pea Plant Experiments </li> <li> Slide 16 </li> <li> 15 Reproduction in Flowering Plants Pollen contains sperm Produced by the stamen Ovary contains eggs Found inside the flower Pollen carries sperm to the eggs for fertilization Self-fertilization can occur in the same flower Cross-fertilization can occur between flowers </li> <li> Slide 17 </li> <li> 16 </li> <li> Slide 18 </li> <li> 17 </li> <li> Slide 19 </li> <li> 18 Mendels Experimental Results </li> <li> Slide 20 </li> <li> 19 Did the observed ratio match the theoretical ratio? The theoretical or expected ratio of plants producing round or wrinkled seeds is 3 round :1 wrinkled Mendels observed ratio was 2.96:1 The discrepancy is due to statistical error The larger the sample the more nearly the results approximate to the theoretical ratio </li> <li> Slide 21 </li> <li> Looking closer at Mendels work true-breeding purple-flower peas true-breeding white-flower peas X 100% purple-flower peas F 1 generation (hybrids) 25% white-flower peas F 2 generation 75% purple-flower peas 3:1 P self-pollinate </li> <li> Slide 22 </li> <li> Test cross Cross-breed the dominant phenotype unknown genotype with a homozygous recessive (pp) to determine the identity of the unknown allele x pp is it PP or Pp? </li> <li> Slide 23 </li> <li> x PPpp Test cross pp P P PpPp PpPpPpPp PpPp pp P p PpPp pp PpPp x PpPp 100% 50%:50% 1:1 </li> <li> Slide 24 </li> <li> 23 Mendels Laws </li> <li> Slide 25 </li> <li> Mendels laws of heredity (#1) Law of segregation when gametes are produced during meiosis, homologous chromosomes separate from each other each allele for a trait is packaged into a separate gamete PP P P pp p p PpPp P p </li> <li> Slide 26 </li> <li> Law of Segregation What meiotic event creates the law of segregation? Meiosis 1 </li> <li> Slide 27 </li> <li> Monohybrid cross Some of Mendels experiments followed the inheritance of single characters flower color seed color monohyb rid crosses Other of Mendels experiments followed the inheritance of 2 different characters seed color and seed shape dihybrid crosses </li> <li> Slide 28 </li> <li> Dihybrid cross true-breeding yellow, round peas true-breeding green, wrinkled peas x YYRRyyrr P YyRr 100% F 1 generation (hybrids) yellow, round peas self-pollinate F 2 generation 9/16 yellow round peas 9:3:3:1 3/16 green round peas 3/16 yellow wrinkled peas 1/16 green wrinkled peas Y = yellow R = round y = green r = wrinkled </li> <li> Slide 29 </li> <li> Dihybrid cross YyRr YRYryR yr YR Yr yR yr YYRRYYRrYyRRYyRr YYRrYYrrYyRrYyrr YyRRYyRryyRRyyRr YyRrYyrryyRryyrr x 9/16 yellow round 3/16 green round 3/16 yellow wrinkled 1/16 green wrinkled </li> <li> Slide 30 </li> <li> Mendels laws of heredity (#2) Law of independent assortment each pair of alleles segregates into gametes independently 4 classes of gametes are produced in equal amounts YR, Yr, yR, yr only true for genes on separate chromosomes YyRr Yr yR YR yr </li> <li> Slide 31 </li> <li> Law of Independent Assortment What meiotic event creates the law of independent assortment? Meiosis 1 </li> <li> Slide 32 </li> <li> The chromosomal basis of Mendels laws Trace the genetic events through meiosis, gamete formation &amp; fertilization to offspring </li> <li> Slide 33 </li> <li> Review: Mendels laws of heredity Law of segregation monohybrid cross single trait each allele segregates into separate gametes established by Meiosis 1 Law of independent assortment dihybrid (or more) cross 2 or more traits each pair of alleles for genes on separate chromosomes segregates into gametes independently established by Meiosis 1 </li> <li> Slide 34 </li> <li> Genetics &amp; Probability Mendels laws: segregation independent assortment reflect same laws of probability that apply to tossing coins or rolling dice </li> <li> Slide 35 </li> <li> Probability &amp; genetics Calculating probability of making a specific gamete is just like calculating the probability in flipping a coin probability of tossing heads? 50% probability making a P gamete PP P P PpPp P p 50% 100% </li> <li> Slide 36 </li> <li> Calculating probability Pp x Pp Pp male / sperm P p female / eggs PP Pppp Pp spermegg 1/2 offspring =x1/4 PPPP 1/2 =x1/4 PpPpPp 1/2 =x1/4 pppp 1/2 =x1/4 1/2 pP </li> <li> Slide 37 </li> <li> Chance that 2 or more independent events will occur together probability that 2 coins tossed at the same time will land heads up probability of Pp x Pp pp Rule of multiplication 1/2 x 1/2 = 1/4 </li> <li> Slide 38 </li> <li> Calculating dihybrid probability Rule of multiplication also applies to dihybrid crosses heterozygous parents YyRr probability of producing yyrr? probability of producing y gamete = 1/2 probability of producing r gamete = 1/2 probability of producing yr gamete = 1/2 x 1/2 = 1/4 probability of producing a yyrr offspring = 1/4 x 1/4 = 1/16 </li> <li> Slide 39 </li> <li> NOW TO PRACTICE! 38 </li> </ul>

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