2 Gregor Mendel 1st person to trace successive generations of living thingsAugustinian Monk – Brunn, Austriataught natural science in high school“How did plants obtain atypical characteristics?”
3 Vocabulary Used in Genetics phenotype: physical expression of a genegenotype: a make of genes in a chromosomeTall = Tshort = tT Tt thomozygous: alleles for a trait are the sameT Theterozygous: alleles for a trait are oppositeTallShortT t
4 More Vocabulary Used in Genetics heredity: passing characteristics from parents to offspringgenetics: study of hereditytraits: inherited characteristics
5 More Vocabulary Used in Genetics gametes: sex cells (sperm and egg)fertilization: uniting of male and female gametespollinization: plant fertilizationzygote: cell produced by fertilizationparent generation: Pfilial = son or daughter: Fallele: factor that controls expression of a trait
6 Mendel’s Findings:Hereditary factors do not combine, but are passed intact to offspring.Each member of the parental generation transmitsonly half of its hereditary factors to each offspring.Certain factors are "dominant" over others.Different offspring of the same parents receivedifferent sets of hereditary factors.Mendel's work became, and still is, the foundation for modern genetics.
7 Mendel's work became, and still is, the foundation for modern genetics.HoweverMendel's work became, and still is,the foundation for modern genetics.
8 Gregor Mendel and the Laws of Genetics I. Why Mendel succeeded:A. used controlled experimentsB. studied only one trait at a timeC. did mathematical analysis of data
9 II. Mendel’s Monohybrid Crosses A. First Generation Cross1. tall pea plants = P12. short pea plants = P13. all offspring were tall = F1
10 B. Second Generation Cross 1. 2 tall offspring from first generation cross = F12. ¾ of these offspring = Tall = F23. ¼ of these offspring = Short = F2
11 C. Mendel’s conclusions: Rules 1. Rule of Unit FactorsEach organism has 2 factors for each of its traits(alleles: gene alternatives)2. Rule of DominanceFor each trait there exists 2 possible factorsthat are expressed in physical characters,one that may be dominant, and the otherrecessive.3. Law of SegregationThe two alleles for each trait must separatewhen gametes form.
12 D. Expression of Traits1. phenotype: physical expression of a gene2. genotype: a make of genes on a chromosome3. homozygous: alleles for a trait are the same4. heterozygous: alleles for a trait are opposite
13 III. Reginald Punnett and the Punnett Squares A. English Biologist1905: devised a shorthand way of findingthe expected proportions of possible genotypesin the offspring of a crossC. Method called: Punnett SquareTakes into account that fertilizationoccurs randomly2. Agrees with Mendel’s law of segregationIf you know the genotype of the parents,you can use a Punnett square to predictthe possible genotypes of their offspring.
16 (cross involving two different traits) IV. Mendel’s Dihybrid Crosses(cross involving two different traits)A. experimenting with plants that had two different traits that differed from each other1. used true-breeding pea plants that hadround yellow seeds (RRYY)2. crossed with true-breeding pea plants thathad wrinkled green seeds (rryy)3. smooth was dominant and wrinkled was recessive4. yellow was dominant and green was recessive
17 true-breeding pea plants that had round yellow seedsround seedsyellow seedsRRYYRRYY
18 true-breeding pea plants that had wrinkled green seeds (rryy) wrinkled seedsgreen seedsrryyrryy
19 true-breeding pea plants that had round yellow seeds wrinkled green seeds+RRYY+(rryy)RRYYrryyorRRrrYYrr
20 P1 R Y R Y R Y R Y R r Y y R r Y y r y R r Y y R r Y y R r Y y R r Y y
21 Result was 100% round yellow seeded plants true-breeding pea plants that hadround yellow seedstrue-breeding pea plants that hadwrinkled green seeds+RRYY+(rryy)Result was 100% round yellow seeded plants
22 Offspring of P1 cross pea plants that had round yellow seeds wrinkled green seeds+RrYy(RrYy)+?Result was different.
23 F1 R Y R y r Y r y R R Y Y r R Y Y R Y R R y Y r R y Y R R Y y r R Y y
25 Genes for different traits are inherited independently of each other. B. F1 generation produced all round yellow seedsC. F2 generation produced9 round yellow3 round green3 wrinkled yellow1 wrinkled greenD. The Law of Independent AssortmentGenes for different traits are inheritedindependently of each other.
32 Dominant Examples Double Recessive Examples Examples Brown Eyes over Blue EyesColor Vision over Color BlindnessHairy Heads over Bald HeadsCurly Tongue over Flat TongueExtra Fingers over Five FingersDouble Recessive Examples ExamplesHemophiliaSickle-Cell DiseaseTay-Sachs DiseaseDwarfism