2 Gregor Mendel Mendel was an Austrian monk. Mendel formulated two fundamental laws of heredity in the early 1860's.He had previously studied science and mathematics (including Statistics) at the University of Vienna. Mendel’s knowledge of statistics later proved valuable in his research on Heredity – the transmission of characteristics from Parent to Offspring.Mendel's work was unrecognized until 1900.
4 Mendel’s ExperimentsA hybrid is the product of parent organisms that are True-Breeding or pure-breeding for different forms of One Trait. Plants that are PURE for a trait always produce offspring with that Trait. The term STRAIN denotes plants that are Pure for a Specific Trait.1. Mendel produced strains by allowing the plants to Self-Pollinate for several generations.2. He eventually obtained 14 strains, one for each of the 14 traits he observed. He called each strain a Parental Generation or P1 generation. This is the parental generation in a breeding experiment.
5 3. He used Cross-pollination between two strains and tracked each trait through two generations. (Monohybrid Cross)4. F1 generation is the first-generation offspring in a breeding experiment. The First Filial Generation.5. F2 generation is the second-generation offspring in a breeding experiment. The Second Filial Generation.6. He also performed reciprocal crosses of pollen on stigmas (e.g. tall-with-short and short-with tall).
6 Mendel’s ConclusionsIn his crosses each trait had a Dominant Factor which masked, or dominated the other factor for a specific trait; the other we call the Recessive Factor.In a true-breeding cross (BBxbb) the recessive factor is masked in F1 but appears in F2
7 Law of Segregation: Each organism contains two factors for each trait; factors segregate in the formation of gametes. When two gametes combine during fertilization, the offspring have two factors controlling a specific trait.Law of Independent Assortment states that factors for different characteristics are distributed to gametes independently.
8 Punnett SquaresPunnett sqaures are used to aid in predicting the probability that certain traits will be inherited by offspringProbability is the likelihood that a specific event will occur or is the likely outcome a given event will occur from random chance
9 Monohybrid Crosses (only one trait) 1. Determine the dominant and Recessive traitWill be stated in the problemie. Black is dominant to white in bunnies
10 2. Assign letters for the trait Dominant trait gets the capital letterRecessive traits gets the lower case letterB = blackb = white
11 3. Determine genotype for parents White male = bbHeterozygous black female = Bb
13 Punnett square holds offspring genotypes B bbGenotype = letter code5. Determine genotype of offspringBbbb
14 6. Determine genotype ratio Count offspring in the Punnett square genotype ratio = 2:20/4 BB2/4 Bb2/4 bb
15 7. Determine phenotype ratio Phenotype = what they look likeCount offspring in the Punnett square phenotype ratio = 2:2*If ratio doesn’t add up to total number of boxes in the punnett square you’ve made a mistake
16 Practice ProblemsA pure-breed white flower crosses with a pure-breed purple flower. Purple is dominant to white.Show the punnet squareWhat is the genotype of the F1 generationWhat is the phenotype of the F1 generation