Presentation on theme: "The Work of Gregor Mendel 1822-1884 1st person to trace successive generations of living things Augustinian Monk – Brunn, Austria taught natural science."— Presentation transcript:
The Work of Gregor Mendel
1st person to trace successive generations of living things Augustinian Monk – Brunn, Austria taught natural science in high school “How did plants obtain atypical characteristics?”
Vocabulary Used in Genetics phenotype: physical expression of a gene genotype: a make of genes in a chromosome homozygous: alleles for a trait are the same heterozygous: alleles for a trait are opposite TallShort Tall = T short = t T T t t T T T t
More Vocabulary Used in Genetics traits: inherited characteristics genetics: study of heredity heredity: passing characteristics from parents to offspring
allele: factor that controls expression of a trait filial = son or daughter: F parent generation: P pollinization: plant fertilization zygote: cell produced by fertilization fertilization: uniting of male and female gametes gametes: sex cells (sperm and egg) More Vocabulary Used in Genetics
Mendel’s Findings Mendel’s Findings : Hereditary factors do not combine, but are passed intact to offspring. Each member of the parental generation transmits only half of its hereditary factors to each offspring. Certain factors are "dominant" over others. Different offspring of the same parents receive different sets of hereditary factors. Mendel's work became, and still is, the foundation for modern genetics.
Mendel's work became, and still is, the foundation for modern genetics. However Mendel's work became, and still is, the foundation for modern genetics.
Gregor Mendel and the Laws of Genetics I.Why Mendel succeeded: A.used controlled experiments B.studied only one trait at a time C.did mathematical analysis of data
II.Mendel’s Monohybrid Crosses A.First Generation Cross 1. tall pea plants = P 1 2. short pea plants = P 1 3. all offspring were tall = F 1
B.Second Generation Cross 1.2 tall offspring from first generation cross = F 1 2.¾ of these offspring = Tall = F 2 3.¼ of these offspring = Short = F 2
C.Mendel’s conclusions: Rules 1.Rule of Unit Factors Each organism has 2 factors for each of its traits (alleles: gene alternatives ) 2.Rule of Dominance For each trait there exists 2 possible factors that are expressed in physical characters, one that may be dominant, and the other recessive. 3.Law of Segregation The two alleles for each trait must separate when gametes form.
D.Expression of Traits 1.phenotype: physical expression of a gene 2.genotype: a make of genes on a chromosome 3.homozygous: alleles for a trait are the same 4.heterozygous: alleles for a trait are opposite
III.Reginald Punnett and the Punnett Squares A.English Biologist B. 1905: devised a shorthand way of finding the expected proportions of possible genotypes in the offspring of a cross C.Method called: Punnett Square 1.Takes into account that fertilization occurs randomly 2. Agrees with Mendel’s law of segregation 3.If you know the genotype of the parents, you can use a Punnett square to predict the possible genotypes of their offspring.
Punnett Square Reginald Punnett 1905
T T T t t tTt tTtT V.Monohybrid Crosses♂♀
IV. IV. Mendel’s Dihybrid Crosses (cross involving two different traits) A. A.experimenting with plants that had two different traits that differed from each other 1. 1.used true-breeding pea plants that had round yellow seeds (RRYY) 2. 2.crossed with true-breeding pea plants that had wrinkled green seeds (rryy) 3. 3.smooth was dominant and wrinkled was recessive 4. 4.yellow was dominant and green was recessive
yellow seeds RRYY round seeds true-breeding pea plants that had round yellow seeds RRYY
green seeds rryy wrinkled seeds rryy true-breeding pea plants that had wrinkled green seeds (rryy)
true-breeding pea plants that had round yellow seeds true-breeding pea plants that had wrinkled green seeds RRYY(rryy) + + RRYYrryy RRrrYYrr or
r r R RY y Y y Y Y y y r r RR R R R R R R R RY Y Y Y Y Y Y YR R R R R R R R Y Y Y YY Y Y Y r r r r r r rr rr r r rrrr y y y y y y yy yy y y yyyyP1
true-breeding pea plants that had round yellow seeds true-breeding pea plants that had wrinkled green seeds RRYY(rryy) + + Result was 100% round yellow seeded plants
Offspring of P1 cross pea plants that had round yellow seeds Offspring of P1 cross pea plants that had wrinkled green seeds RrYy(RrYy) + + Result was different. ?
R R R RY Y Y Y y y y y r r rr R R R R R R R RY Y Y Y Y Y Y Yr r r r r r r r y y y yy y y y R R R R R R RR rr r r rrrr Y Y Y Y y y yy YY Y Y yyyy F1
B.F 1 generation produced all round yellow seeds C.F 2 generation produced 9 round yellow D.The Law of Independent Assortment Genes for different traits are inherited independently of each other. 3 round green 3 wrinkled yellow 1 wrinkled green
S-phase of cell cycle 2n x 2
Meiosis I 2n x 2 2n 2n A B
Meiosis II 2n n n A
2n n n B
Dominant Examples Brown Eyes over Blue Eyes Color Vision over Color Blindness Hairy Heads over Bald Heads Curly Tongue over Flat Tongue Extra Fingers over Five Fingers Double Recessive Examples Examples Hemophilia Sickle-Cell Disease Tay-Sachs Disease Dwarfism
VI. Genetic Variation
VII. Crossing Over
VIII. NONDISJUNCTION Normal distribution of chromosomes during meiosis.